Lightguide including a film with one or more bends

ABSTRACT

A lightguide includes a film including a body having a light emitting region and a light mixing region adjacent the light emitting region. A first bend with a first diameter in a first plane is formed in the film within the light mixing region, wherein a first portion of the light mixing region is positioned behind the light emitting region. A second bend is formed in the film within the light mixing region.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.61/777,632 entitled “Illumination Device Including a Frame and a Filmwith One or More Bends,” filed on Mar. 12, 2013, which is incorporatedby reference herein in its entirety.

TECHNICAL FIELD

The subject matter disclosed herein generally relates to lightguides,films, and light emitting devices such as, without limitation, lightfixtures, backlights, frontlights, light emitting signs, passivedisplays, and active displays and their components and methods ofmanufacture.

BACKGROUND

Conventionally, in order to reduce the thickness of displays andbacklights, edge-lit configurations using rigid lightguides have beenused to receive light from the edge of and direct light out of a largerarea face. These types of light emitting devices are typically housed inrelatively thick, rigid frames that do not allow for component or deviceflexibility and require long lead times for design changes. The volumeof these devices remains large and often includes thick or large framesor bezels around the device. The thick lightguides (typically 2millimeters (mm) and larger) limit the design configurations, productionmethods, and illumination modes. The ability to further reduce thethickness and overall volume of these area light emitting devices hasbeen limited by the ability to couple sufficient light flux into athinner lightguide.

SUMMARY

In one aspect, a lightguide includes a film including a body having afirst surface and an opposing second surface and a plurality of couplinglightguides extending from the body. Each coupling lightguide of theplurality of coupling lightguides has an end. The plurality of couplinglightguides are folded and stacked such that the ends of the pluralityof coupling lightguides define a light input surface. The body of thefilm includes a light emitting region defined by a plurality of lightextracting features and a light mixing region positioned between theplurality of coupling lightguides and the light emitting region. Thelight mixing region is folded behind the light emitting region at afirst bend with a first bend diameter in a first plane, wherein thefirst bend diameter is greater than an average separation between thefirst surface of the film within the light emitting region and the firstsurface of the film within the light mixing region positioned behind thelight emitting region.

In another aspect, a lightguide includes a film including a bodycomprising a light emitting region and a light mixing region adjacentthe light emitting region. A first bend is formed in the film within thelight mixing region having a first diameter in a first plane, wherein afirst portion of the light mixing region is positioned behind the lightemitting region. A second bend is formed in the film within the lightmixing region, wherein a second portion of the light mixing region ispositioned at a distance from the light emitting region less than thefirst diameter.

In yet another aspect, a lightguide includes a film including a bodycomprising a light emitting region and a light mixing region adjacentthe light emitting region. A first bend with a first diameter in a firstplane is formed in the film within the light mixing region, wherein afirst portion of the light mixing region is positioned behind the lightemitting region. A second bend is formed in the film within the lightmixing region.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of one embodiment of a light emitting deviceincluding a light input coupler disposed on one side of a lightguide.

FIG. 2 is a side view of one embodiment of a light emitting deviceincluding a film-based lightguide operatively coupled to a frame.

FIG. 3 is a side view of the light emitting device of FIG. 2illustrating the relative position maintaining element between the twotabs of the frame.

FIG. 4 is a bottom perspective view of one embodiment of a frame and arelative position maintaining element suitable for use in an embodimentof a light emitting device.

FIG. 5 is a top perspective view of the frame of FIG. 4.

FIG. 6 is a perspective view of one embodiment of a frame includingopenings suitable for use in a light emitting device.

FIG. 7 is a perspective view of the frame of FIG. 6, a first relativeposition maintaining element, and a second relative position maintainingelement.

FIG. 8 is a side view of one embodiment of a light emitting deviceincluding a film-based lightguide including a plurality of bendsoperatively coupled to a frame.

FIG. 9 is side view of the lightguide including the light emittingregion, the light mixing region and the relative position maintainingelement of FIG. 8.

FIG. 10 is a side view of one embodiment of a light emitting deviceincluding a film-based lightguide including two bends operativelycoupled to a frame.

FIG. 11 is a side view of one embodiment of a light emitting deviceincluding a film-based lightguide with 3 bends operatively coupled to aframe.

FIG. 12 is a bottom view of one embodiment of a frame, a first relativeposition maintaining element, and a second relative position maintainingelement suitable for use in an embodiment of a light emitting device.

FIG. 13 is a bottom view of one embodiment of a frame, a first relativeposition maintaining element, a second relative position maintainingelement, a third relative position maintaining element, and a fourthrelative position maintaining element suitable for use in an embodimentof a light emitting device.

FIG. 14 is a side view of one embodiment of a reflective display with afilm lightguide and a guide with a guide surface adjacent a surface ofthe film lightguide with an subtended angle of 90 degrees.

FIG. 15 is a side view of one embodiment of a reflective display with afilm lightguide and a guide with a guide surface adjacent a surface ofthe film lightguide with an subtended angle of 180 degrees.

FIG. 16 is a side view of one embodiment of a reflective display with afilm lightguide and a guide with a guide surface adjacent a surface ofthe film lightguide with an subtended angle of 270 degrees.

DETAILED DESCRIPTION

The features and other details of several embodiments will now be moreparticularly described. It will be understood that particularembodiments described herein are shown by way of illustration and not aslimitations. The principal features can be employed in variousembodiments without departing from the scope of any particularembodiment. All parts and percentages are by weight unless otherwisespecified.

DEFINITIONS

“Electroluminescent display” is defined herein as a means for displayinginformation wherein the legend, message, image or indicia thereon isformed by or made more apparent by an electrically excitable source ofillumination. This includes illuminated cards, transparencies, pictures,printed graphics, fluorescent signs, neon signs, channel letter signs,light box signs, bus-stop signs, illuminated advertising signs, EL(electroluminescent) signs, LED signs, edge-lit signs, advertisingdisplays, liquid crystal displays, electrophoretic displays, point ofpurchase displays, directional signs, illuminated pictures, and otherinformation display signs. Electroluminescent displays can beself-luminous (emissive), back-illuminated (back-lit), front illuminated(front-lit), edge-illuminated (edge-lit), waveguide-illuminated or otherconfigurations wherein light from a light source is directed throughstatic or dynamic means for creating images or indicia.

“Optically coupled” as defined herein refers to coupling of two or moreregions or layers such that the luminance of light passing from oneregion to the other is not substantially reduced by Fresnel interfacialreflection losses due to differences in refractive indices between theregions. “Optical coupling” methods include methods of coupling whereinthe two regions coupled together have similar refractive indices orusing an optical adhesive with a refractive index substantially near orbetween the refractive index of the regions or layers. Examples of“optical coupling” include, without limitation, lamination using anindex-matched optical adhesive, coating a region or layer onto anotherregion or layer, or hot lamination using applied pressure to join two ormore layers or regions that have substantially close refractive indices.Thermal transferring is another method that can be used to opticallycouple two regions of material. Forming, altering, printing, or applyinga material on the surface of another material are other examples ofoptically coupling two materials. “Optically coupled” also includesforming, adding, or removing regions, features, or materials of a firstrefractive index within a volume of a material of a second refractiveindex such that light propagates from the first material to the secondmaterial. For example, a white light scattering ink (such as titaniumdioxide in a methacrylate, vinyl, or polyurethane based binder) may beoptically coupled to a surface of a polycarbonate or silicone film byinkjet printing the ink onto the surface. Similarly, a light scatteringmaterial such as titanium dioxide in a solvent applied to a surface mayallow the light scattering material to penetrate or adhere in closephysical contact with the surface of a polycarbonate or silicone filmsuch that it is optically coupled to the film surface or volume.

“Lightguide” or “waveguide” refers to a region bounded by the conditionthat light rays propagating at an angle that is larger than the criticalangle will reflect and remain within the region. In a lightguide, thelight will reflect or TIR (totally internally reflect) if the angle (α)satisfies the condition α>sin⁻¹(n₂/n₁), where n₁ is the refractive indexof the medium inside the lightguide and n₂ is the refractive index ofthe medium outside the lightguide. Typically, n₂ is air with arefractive index of n≈1; however, high and low refractive indexmaterials can be used to achieve lightguide regions. A lightguide doesnot need to be optically coupled to all of its components to beconsidered as a lightguide. Light may enter from any face (orinterfacial refractive index boundary) of the waveguide region and maytotally internally reflect from the same or another refractive indexinterfacial boundary. A region can be functional as a waveguide orlightguide for purposes illustrated herein as long as the thickness islarger than the wavelength of light of interest. For example, alightguide may be a 5 micron region or layer of a film or it may be a 3millimeter sheet including a light transmitting polymer.

“In contact” and “disposed on” are used generally to describe that twoitems are adjacent one another such that the whole item can function asdesired. This may mean that additional materials can be present betweenthe adjacent items, as long as the item can function as desired.

“Adjacent” is generally used to refer to an element that is located nextto or in contact with an adjacent element without an objecttherebetween. In the context of this application, adjacent may includean air gap between two adjacent elements or the elements may becontacting each other.

A “film” as used herein refers to a thin extended region, membrane, orlayer of material.

A “bend” as used herein refers to a deformation or transformation inshape by the movement of a first region of an element relative to asecond region, for example. Examples of bends include the bending of aclothes rod when heavy clothes are hung on the rod or rolling up a paperdocument to fit it into a cylindrical mailing tube. A “fold” as usedherein is a type of bend and refers to the bend or lay of one region ofan element toward a second region such that the first region covers atleast a portion of the second region. An example of a fold includesbending a letter and forming creases to place it in an envelope. A folddoes not require that all regions of the element overlap. A bend or foldmay be a change in the direction along a first direction along a surfaceof the object. A fold or bend may or may not have creases and the bendor fold may occur in one or more directions or planes such as 90 degreesor 45 degrees. A bend or fold may be lateral, vertical, torsional, or acombination thereof.

Light Emitting Device

In one embodiment, a light emitting device includes a first lightsource, a light input coupler, a light mixing region, and a lightguideincluding a light emitting region with a light extraction feature. Inone embodiment, the first light source has a first light source emittingsurface, the light input coupler includes an input surface disposed toreceive light from the first light source and transmit the light throughthe light input coupler by total internal reflection through a pluralityof coupling lightguides. In this embodiment, light exiting the couplinglightguides is re-combined and mixed in a light mixing region anddirected through total internal reflection within a lightguide orlightguide region. Within the lightguide, a portion of incident light isdirected within the light extracting region by light extracting featuresinto a condition whereupon the angle of light is less than the criticalangle for the lightguide and the directed light exits the lightguidethrough the lightguide light emitting surface.

In a further embodiment, the lightguide is a film with light extractingfeatures below a light emitting device output surface within the film.The film is separated into coupling lightguide strips which are foldedsuch that the coupling lightguide strips form a light input coupler witha first input surface formed by the collection of edges of the couplinglightguide strips.

In one embodiment, the light emitting device has an optical axis definedherein as the direction of peak luminous intensity for light emittingfrom the light emitting surface or region of the device for devices withoutput profiles with one peak. For optical output profiles with morethan one peak and the output is symmetrical about an axis, such as witha “batwing” type profile, the optical axis of the light emitting deviceis the axis of symmetry of the light output. In light emitting deviceswith angular luminous intensity optical output profiles with more thanone peak which are asymmetrical about an axis, the light emitting deviceoptical axis is the angular weighted average of the luminous intensityoutput. For non-planar output surfaces, the light emitting deviceoptical axis is evaluated in two orthogonal output planes and may be aconstant direction in a first output plane and at a varying angle in asecond output plane orthogonal to the first output plane. For example,light emitting from a cylindrical light emitting surface may have a peakangular luminous intensity (thus light emitting device optical axis) ina light output plane that does not include the curved output surfaceprofile and the angle of luminous intensity could be substantiallyconstant about a rotational axis around the cylindrical surface in anoutput plane including the curved surface profile. Thus, in thisexample, the peak angular intensity is a range of angles. When the lightemitting device has a light emitting device optical axis in a range ofangles, the optical axis of the light emitting device includes the rangeof angles or an angle chosen within the range. The optical axis of alens or element is the direction of which there is some degree ofrotational symmetry in at least one plane and as used herein correspondsto the mechanical axis. The optical axis of the region, surface, area,or collection of lenses or elements may differ from the optical axis ofthe lens or element, and as used herein is dependent on the incidentlight angular and spatial profile, such as in the case of off-axisillumination of a lens or element.

Various light emitting devices, components or layers of light emittingdevices, displays, electroluminescent displays, their methods ofmanufacture, and their configurations can be used with embodimentsdisclosed herein and include those disclosed in U.S. patent applicationSer. No. 13/088,167, which is incorporated by reference herein in itsentirety.

Light Input Coupler

In one embodiment, a light input coupler includes a plurality ofcoupling lightguides disposed to receive light emitting from a lightsource and channel the light into a lightguide. In one embodiment, theplurality of coupling lightguides are strips cut from a lightguide filmsuch that each coupling lightguide strip remains un-cut on at least oneedge but can be rotated or positioned (or translated) substantiallyindependently from the lightguide to couple light through at least oneedge or surface of the strip. In another embodiment, the plurality ofcoupling lightguides are not cut from the lightguide film and areseparately optically coupled to the light source and the lightguide. Inanother embodiment, the light emitting device includes a light inputcoupler having a core region of a core material and a cladding region orcladding layer of a cladding material on at least one face or edge ofthe core material with a refractive index less than a refractive indexof the core material. In other embodiment, the light input couplerincludes a plurality of coupling lightguides wherein a portion of lightfrom a light source incident on a face of at least one strip is directedinto the lightguide such that light travels in a waveguide condition.The light input coupler may also include one or more of the following: astrip folding device, a strip holding element, and an input surfaceoptical element.

In one embodiment, a first array of light input couplers is positionedto input light into the light mixing region, light emitting region, orlightguide region and a separation distance between the light inputcouplers varies. In one embodiment, a light emitting device includes atleast three light input couplers disposed along a side of a film havinga separation distance between a first pair of input couplers along theside of the film different than a separation distance between a secondpair of input couplers along the side of the film. For example, in oneembodiment a separation distance between the first pair of inputcouplers along the side of the film is great than a separation distancebetween a second pair of input couplers along the side of the film.

Light Source

In one embodiment, a light emitting device includes at least one lightsource selected from a group: fluorescent lamp, cylindrical cold-cathodefluorescent lamp, flat fluorescent lamp, light emitting diode, organiclight emitting diode, field emissive lamp, gas discharge lamp, neonlamp, filament lamp, incandescent lamp, electroluminescent lamp,radiofluorescent lamp, halogen lamp, incandescent lamp, mercury vaporlamp, sodium vapor lamp, high pressure sodium lamp, metal halide lamp,tungsten lamp, carbon arc lamp, electroluminescent lamp, laser, photonicbandgap based light source, quantum dot based light source, highefficiency plasma light source, microplasma lamp. The light emittingdevice may include a plurality of light sources arranged in an array, onopposite sides of lightguide, on orthogonal sides of a lightguide, on 3or more sides of a lightguide, or on 4 sides of a substantially planerlightguide. The array of light sources may be a linear array withdiscrete LED packages includes at least one LED die. In anotherembodiment, a light emitting device includes a plurality of lightsources within one package disposed to emit light toward a light inputsurface. In one embodiment, the light emitting device includes 1, 2, 3,4, 5, 6, 8, 9, 10, or more than 10 light sources. In another embodiment,the light emitting device includes an organic light emitting diodedisposed to emit light as a light emitting film or sheet. In anotherembodiment, the light emitting device includes an organic light emittingdiode disposed to emit light into a lightguide.

Led Array

In one embodiment, the light emitting device includes a plurality ofLEDs or LED packages wherein the plurality of LEDs or LED packagesincludes an array of LEDs. The array components (LEDs or electricalcomponents) may be physically (and/or electrically) coupled to a singlecircuit board or they may be coupled to a plurality of circuit boardsthat may or may not be directly physically coupled (i.e. such as not onthe same circuit board). In one embodiment, the array of LEDs is anarray including at least two selected from the group: red, green, blue,and white LEDs. In this embodiment, the variation in the white point dueto manufacturing or component variations can be reduced. In anotherembodiment, the LED array includes at least one cool white LED and onered LED. In this embodiment, the CRI, or Color Rendering Index, ishigher than the cool white LED illumination alone.

Led Array Location

In one embodiment, a plurality of LED arrays are disposed to couplelight into a single light input coupler or more than one light inputcoupler. In a further embodiment, a plurality of LEDs disposed on acircuit board are disposed to couple light into a plurality of lightinput couplers that direct light toward a plurality of sides of a lightemitting device including a light emitting region. In a furtherembodiment, a light emitting device includes an LED array and lightinput coupler folded behind the light emitting region of the lightemitting device such that the LED array and light input coupler are notvisible when viewing the center of the light emitting region at an angleperpendicular to the surface. In another embodiment, a light emittingdevice includes a single LED array disposed to couple light into atleast one light input coupler disposed to direct light into the lightemitting region from the bottom region of a light emitting device. Inone embodiment, a light emitting device includes a first LED array and asecond LED array disposed to couple light into a first light inputcoupler and a second light input coupler, respectively, wherein thefirst light input coupler and second light input coupler are disposed todirect light into the light emitting region from the top region andbottom region, respectively, of a light emitting device. In a furtherembodiment, a light emitting device includes a first LED array, a secondLED array, and a third LED array, disposed to couple light into a firstlight input coupler, a second light input coupler, and a third lightinput coupler, respectively, disposed to direct light into the lightemitting region from the bottom region, left region, and right region,respectively, of a light emitting device. In another embodiment, a lightemitting device includes a first LED array, a second LED array, a thirdLED array, and a fourth LED array, disposed to couple light into a firstlight input coupler, a second light input coupler, a third light inputcoupler, and a fourth light input coupler, respectively, disposed todirect light into the light emitting region from the bottom region, leftregion, right region, and top region, respectively, of a light emittingdevice.

Wavelength Conversion Material

In another embodiment, the LED is a blue or ultraviolet LED combinedwith a phosphor. In another embodiment, a light emitting device includesa light source with a first activating energy and a wavelengthconversion material which converts a first portion of the firstactivating energy into a second wavelength different than the first. Inanother embodiment, the light emitting device includes at least onewavelength conversion material selected from the group: a fluorophore,phosphor, a fluorescent dye, an inorganic phosphor, photonic bandgapmaterial, a quantum dot material, a fluorescent protein, a fusionprotein, a fluorophores attached to protein to specific functionalgroups (such as amino groups (active ester, carboxylate, isothiocyanate,hydrazine), carboxyl groups (carbodiimide), thiol (maleimide, acetylbromide), azide (via click chemistry or non-specifically(glutaraldehyde))), quantum dot fluorophores, small moleculefluorophores, aromatic fluorophores, conjugated fluorophores, afluorescent dye, and other wavelength conversion material.

In one embodiment, the light source includes a semiconductor lightemitter such as an LED and a wavelength conversion material thatconverts a portion of the light from the emitter to a shorter or longerwavelength. In another embodiment, at least one selected from the group:light input coupler, cladding region, coupling lightguide, input surfaceoptic, coupling optic, light mixing region, lightguide, light extractionfeature or region, and light emitting surface includes a wavelengthconversion material.

Light Input Coupler Input Surface

In one embodiment, the light input coupler includes a collection ofcoupling lightguides with a plurality of edges forming a light couplerinput surface. In another embodiment, an optical element is disposedbetween the light source and at least one coupling lightguide whereinthe optical element receives light from the light source through a lightcoupler input surface. In some embodiments, the input surface issubstantially polished, flat, or optically smooth such that light doesnot scatter forwards or backwards from pits, protrusions or other roughsurface features. In some embodiments, an optical element is disposed tobetween the light source and at least one coupling lightguide to providelight redirection as an input surface (when optically coupled to atleast one coupling lightguide) or as an optical element separate oroptically coupled to at least one coupling lightguide such that morelight is redirected into the lightguide at angles greater than thecritical angle within the lightguide than would be the case without theoptical element or with a flat input surface. The coupling lightguidesmay be grouped together such that the edges opposite the lightguideregion are brought together to form an input surface including theirthin edges.

Stacked Strips or Segments of Film Forming a Light Input Coupler

In one embodiment, the light input coupler is region of a film thatincludes the lightguide and the light input coupler which includes stripsections of the film which form coupling lightguides that are groupedtogether to form a light coupler input surface. The coupling lightguidesmay be grouped together such the edges opposite the lightguide regionare brought together to form an input surface including their thinedges. A planar input surface for a light input coupler can providebeneficial refraction to redirect a portion of the input light from thesurface into angles such that it propagates at angles greater than thecritical angle for the lightguide. In another embodiment, asubstantially planar light transmitting element is optically coupled tothe grouped edges of coupling lightguides. One or more of the edges ofthe coupling lightguides may be polished, melted, smoothed using acaustic or solvent material, adhered with an optical adhesive, solventwelded, or otherwise optically coupled along a region of the edgesurface such that the surface is substantially polished, smooth, flat,or substantially planarized.

Light Redirecting Optical Element

In one embodiment, a light redirecting optical element is disposed toreceive light from at least one light source and redirect the light intoa plurality of coupling lightguides. In another embodiment, the lightredirecting optical element is at least one selected from the group:secondary optic, mirrored element or surface, reflective film such asaluminized PET, giant birefringent optical films such as Vikuiti™Enhanced Specular Reflector Film by 3M Inc., curved mirror, totallyinternally reflecting element, beamsplitter, and dichroic reflectingmirror or film.

Light Collimating Optical Element

In one embodiment, the light input coupler includes a light collimatingoptical element. A light collimating optical element receives light fromthe light source with a first angular full-width at half maximumintensity within at least one input plane and redirects a portion of theincident light from the light source such that the angular full-width athalf maximum intensity of the light is reduced in the first input plane.In one embodiment, the light collimating optical element is one or moreof the following: a light source primary optic, a light source secondaryoptic, a light input surface, and an optical element disposed betweenthe light source and at least one coupling lightguide. In anotherembodiment, the light collimating element is one or more of thefollowing: an injection molded optical lens, a thermoformed opticallens, and a cross-linked lens made from a mold. In another embodiment,the light collimating element reduces the angular full-width at halfmaximum (FWHM) intensity within the input plane and a plane orthogonalto the input plane.

In one embodiment, a light emitting device includes a light inputcoupler and a film-based lightguide. In one embodiment the light inputcoupler includes a light source and a light collimating optical elementdisposed to receive light from one or more light sources and providelight output in a first output plane, second output plane orthogonal tothe first plane, or in both output planes with an angular full-width athalf maximum intensity in air less than one selected from the group: 60degrees, 40 degrees, 30 degrees, 20 degrees, and 10 degrees from theoptical axis of the light exiting the light collimating optical element.

Coupling Lightguides

In one embodiment, the coupling lightguide is a region wherein lightwithin the region can travel in a waveguide condition and a portion ofthe light input into a surface or region of the coupling lightguidespasses through the coupling lightguide toward a lightguide or lightmixing region. The coupling lightguide, in some embodiments, may serveto geometrically transform a portion of the flux from a light sourcefrom a first shaped area to a second shaped area different from thefirst shaped area. In an example of this embodiment, the light inputsurface of the light input coupler formed from the edges of foldedstrips (coupling lightguides) of a planar film has dimensions of arectangle that is 3 millimeters by 2.7 millimeters and the light inputcoupler couples light into a planar section of a film in the lightmixing region with a cross-sectional dimensions of 40.5 millimeters by0.2 millimeters.

Coupling Lightguide Folds and Bends

In one embodiment, a light emitting device includes a light mixingregion disposed between a lightguide and strips or segments cut to formcoupling lightguides, whereby a collection of edges of the strips orsegments are brought together to form a light input surface of the lightinput coupler disposed to receive light from a light source. In oneembodiment, the light input coupler includes a coupling lightguidewherein the coupling lightguide includes at least one fold or bend in aplane such that at least one edge overlaps another edge. In anotherembodiment, the coupling lightguide includes a plurality of folds orbends wherein edges of the coupling lightguide can be abutted togetherin region such that the region forms a light input surface of the lightinput coupler of the light emitting device. In one embodiment, at leastone coupling lightguide includes a strip or a segment that is bent orfolded to radius of curvature of less than 75 times a thickness of thestrip or the segment. In another embodiment, at least one couplinglightguide includes a strip or a segment that is bended or folded toradius of curvature greater than 10 times a thickness of the strip orthe segment. In another embodiment, at least one coupling lightguide isbent or folded such that a longest dimension in a cross-section throughthe light emitting device or coupling lightguide in at least one planeis less than without the fold or bend. Segments or strips may be bent orfolded in more than one direction or region and the directions offolding or bending may be different between strips or segments.

Coupling Lightguide Lateral Edges

In one embodiment, the lateral edges, defined herein as the edges of thecoupling lightguide which do not substantially receive light directlyfrom the light source and are not part of the edges of the lightguideregion. The lateral edges of the coupling lightguide receive lightsubstantially only from light propagating within the couplinglightguide. In one embodiment, the lateral edges are at least oneselected from the group: uncoated, coated with a reflecting material,disposed adjacent to a reflecting material, and cut with a specificcross-sectional profile. The lateral edges may be coated, bonded to ordisposed adjacent to a specularly reflecting material, partiallydiffusely reflecting material, or diffuse reflecting material. In oneembodiment, the edges are coated with a specularly reflecting inkincluding nano-sized or micron-sized particles or flakes whichsubstantially reflect the light in a specular manner when the couplinglightguides are brought together from folding or bending.

Width of the Coupling Lightguides

In one embodiment, the dimensions of the coupling lightguides aresubstantially equal in width and thickness to each other such that theinput surface areas for each edge surface are substantially the same. Inanother embodiment, at least one selected from the group: couplinglightguide width, the largest width of a coupling waveguide, the averagewidth of the coupling lightguides, and the width of each couplinglightguides is selected from a group of: 0.5 mm-1 mm, 1 mm-2 mm, 2 mm-3mm, 3 mm-4 mm, 5 mm-6 mm, 0.5 mm-2 mm, 0.5 mm-25 mm, 0.5 mm-10 mm, 10-37mm, and 0.5 mm-5 mm. In one embodiment, at least one selected from thegroup: the coupling lightguide width, the largest width of a couplingwaveguide, the average width of the coupling lightguides, and the widthof each coupling lightguides is less than 20 millimeters.

Separation Between the Lightguide Region Edge and the CouplingLightguide Nearest the Edge

In one embodiment, a coupling lightguide nearest the edge of thefilm-based lightguide is spaced from the edge of the film adjacent theside. For example, in one embodiment, the first coupling lightguidealong a side of a film-based lightguide is separated from the edge ofthe lightguide region by a distance greater than 1 mm. In anotherembodiment, the first coupling lightguide along a side of a film-basedlightguide is separated from the edge of the lightguide region by adistance greater than one selected from the group: 0.5, 1, 2, 4, 6, 8,10, 20, and 50 millimeters. In one embodiment, the distance between thelightguide region edge and the first coupling lightguide along a sideimproves the uniformity in the lightguide region due to the light fromthe first coupling lightguide reflecting from the lateral edge of thelightguide region.

Shaped or Tapered Coupling Lightguides

The width of the coupling lightguides may vary in a predeterminedpattern. In one embodiment, the width of the coupling lightguides variesfrom a large width in a central coupling lightguide to smaller width inlightguides further from the central coupling lightguide as viewed whenthe light input edges of the coupling lightguides are disposed togetherto form a light input surface on the light input coupler. In thisembodiment, a light source with a substantially circular light outputaperture can couple into the coupling lightguides such that the light athigher angles from the optical axis are coupled into a smaller widthstrip such that the uniformity of the light emitting surface along theedge of the lightguide or lightguide region and parallel to the inputedge of the lightguide region disposed to receive the light from thecoupling lightguides is greater than one selected from the group: 60%,70%, 80%, 90% and 95%.

Other shapes of stacked coupling lightguides can be envisioned, such astriangular, square, rectangular, oval, etc. that provide matched inputareas to the light emitting surface of the light source. The widths ofthe coupling lightguides may also be tapered such that they redirect aportion of light received from the light source. The lightguides may betapered near the light source, in the area along the coupling lightguidebetween the light source and the lightguide region, near the lightguideregion, or some combination thereof.

The shape of a coupling lightguide is referenced herein from thelightguide region or light emitting region or body of the lightguide.One or more coupling lightguides extending from a side or region of thelightguide region may expand (widen or increase in width) or taper(narrow or decrease in width) in the direction toward the light source.In one embodiment, coupling lightguides taper in one or more regions toprovide redirection or partial collimation of the light traveling withinthe coupling lightguides from the light source toward the lightguideregion. In one embodiment, one or more coupling lightguides widens alongone lateral edge and tapers along the opposite lateral edge. In thisembodiment, the net effect may be that the width remains constant. Thewidening or tapering may have different profiles or shapes along eachlateral side for one or more coupling lightguides. The widening,tapering, and the profile for each lateral edge of each couplinglightguide may be different and may be different in different regions ofthe coupling lightguide. For example, one coupling lightguide in anarray of coupling lightguides may have a parabolic tapering profile onboth sides of the coupling lightguides in the region near the lightsource to provide partial collimation, and at the region starting atabout 50% of the length of the coupling lightguides one lateral edgetapers in a linear angle and the opposite side includes a parabolicshaped edge. The tapering, widening, shape of the profile, location ofthe profile, and number of profiles along each lateral edge may be usedto provide control over one or more selected from the group: spatial orangular color uniformity of the light exiting the coupling lightguidesinto the light mixing region (or light emitting region), spatial orangular luminance uniformity of the light exiting the couplinglightguides into the light mixing region (or light emitting region),angular redirection of light into the light mixing region (or lightemitting region) of the lightguide (which can affect the angular lightoutput profile of the light exiting the light emitting region along withthe shape, size, and type of light extraction features), relative fluxdistribution within the light emitting region, and other lightredirecting benefits such as, without limitation, redirecting more lighttoward a second, extending light emitting region.

Interior Light Directing Edge

In one embodiment, the interior region of one or more couplinglightguides includes an interior light directing edge. The interiorlight directing edge may be formed by cutting or otherwise removing aninterior region of the coupling lightguide. In one embodiment, theinterior light directed edge redirects a first portion of light withinthe coupling lightguide. In one embodiment, the interior light directingedges provide an additional level of control for directing the lightwithin the coupling lightguides and can provide light fluxredistribution within the coupling lightguide and within the lightguideregion to achieve a predetermined light output pattern (such as higheruniformity or higher flux output) in a specific region.

In one embodiment, at least one interior light directing edge ispositioned within a coupling lightguide to receive light propagatingwithin the coupling lightguide within a first angular range from theoptical axis of light traveling within the coupling lightguide anddirect the light to a second, different angular range propagating withinthe coupling lightguide. In one embodiment, the first angular range isselected from the group: 70-89, 70-80, 60-80, 50-80, 40-80, 30-80,20-80, 30-70, and 30-60 degrees; and the second angular range isselected from the group: 0-10, 0-20, 0-30, 0-40, 0-50, 10-40, and 20-60degrees. In one embodiment, a plurality of interior light directingedges are formed after the coupling lightguides are stacked. In anotherembodiment, one or more coupling lightguides have interior lightdirecting edges that form a channel that spatially separates lighttraveling within the coupling lightguide. In one embodiment, a lengthalong the optical axis of light travelling within the couplinglightguide of one or more interior light directing edges is greater thanone selected from the group: 20%, 30%, 40%, 50%, 60%, 70%, 80%, and 90%of a length from an input surface of the coupling lightguide to thelightguide region or the light mixing region along the optical axis oflight traveling within the coupling lightguide. In another embodiment,one or more coupling lightguides have interior light directing edgespositioned within one selected from the group: 1, 5, 7, 10, 15, 20, 25millimeters from the lightguide region of the film-based lightguide. Inone embodiment, one or more coupling lightguides have interior lightdirecting edges positioned within one selected from the group: 1, 5, 7,10, 15, 20, 25 millimeters from the light input surface of the one ormore coupling lightguides. In a further embodiment, one or more couplinglightguides have at least one interior light directing edge with a widthof the interior light directing edge in a direction parallel to the foldline greater than one selected from the group of: 5, 10, 15, 20, 25, 30,35, 40, 45, 50, and 60 percent of a width of the coupling lightguide atthe lightguide region. In a further embodiment, at least one couplinglightguide has two adjacent interior light directing edges wherein theaverage separation between the interior light directing edges in adirection parallel to a fold line is greater than one selected from thegroup of: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, and 60 percent of thewidth of the coupling lightguide at the lightguide region.

In another embodiment, at least one coupling lightguide includes aplurality of channels defined by at least one interior light directingedge and a lateral edge of the coupling lightguide. In a furtherembodiment, the coupling lightguide includes a channel defined by afirst interior light directing edge and a second interior lightdirecting edge. In one embodiment, one or more channels defined byinterior light directing edges and/or lateral edges of the couplinglightguide separate angular ranges of light from the light source intospatially separated channels that can transfer the spatial separation tothe lightguide region. In one embodiment, the channels are parallel tothe extended direction of an array of coupling lightguides. In anotherembodiment, the light source includes a plurality of light emittingdiodes formed in an array such that the optical axis of a first lightsource enters a first channel defined in a coupling lightguide and theoptical axis of a second source enters a second channel defined in acoupling lightguide. In one embodiment, one or more interior lightdirecting edges extend from within one or more coupling lightguides intothe lightguide region of the lightguide. In another embodiment, thelightguide region has one or more interior light directing edges. In afurther embodiment, the lightguide region has one or more interior lightdirecting edges and one or more coupling lightguides include one or moreinterior light directing edges. In another embodiment, one or moreinterior light directing edges extend from within one or more couplinglightguides into the light emitting region of the lightguide. In thisembodiment, for example, a light source including red, green, and bluelight emitting diodes in a linear array adjacent a first, second, andthird channel of a plurality of coupling lightguides, respectively canbe directed to an alternating first, second, and third pixel regionwithin the light emitting region to create a spatial arrangement ofrepeating red, green, blue, red, green, blue, red, green, blue colorpixels in a light emitting region for a color display or sign. Inanother embodiment, the interior region of the light mixing region orlightguide region includes at least one interior light directing edge.

Coupling Lightguide Orientation Angle

In a further embodiment, at least one portion of the array of couplinglightguides is disposed at a first coupling lightguide orientation angleto the edge of at least one of the light mixing region and lightemitting region which it directs light into. The coupling lightguideorientation angle is defined as the angle between the couplinglightguide axis and the direction parallel to the major component of thedirection of the coupling lightguides to the light emitting region ofthe lightguide. The major component of the direction of the couplinglightguide to the light emitting region of the lightguide is orthogonalto the array direction of the array of coupling lightguides at the lightmixing region (or lightguide region if they extend directly from thelight emitting region). In one embodiment, the orientation angle of acoupling lightguide or the average orientation angle of a plurality ofcoupling lightguides is at least one selected from the group: 1-10degrees, 10-20 degrees, 20-30 degrees, 30-40 degrees, 40-50 degrees,60-70 degrees, 70-80 degrees, 1-80 degrees, 10-70 degrees, 20-60degrees, 30-50 degrees, greater than 5 degrees, greater than 10 degrees,and greater than 20 degrees.

Non-Folded Coupling Lightguide

In a further embodiment, the film-based lightguide includes a non-foldedcoupling lightguide disposed to receive light from the light inputsurface and direct light toward the lightguide region without turningthe light. In one embodiment, the non-folded lightguide is used inconjunction with one or more light turning optical elements, lightcoupling optical elements, coupling lightguides with light turningedges, or coupling lightguides with collimating edges. For example, alight turning optical element may be disposed above or below anon-folded coupling lightguide such that a first portion of light from alight source substantially maintains the direction of its optical axiswhile passing through the non-folded coupling lightguide and the lightfrom the source received by the light turning optical element is turnedto enter into a stacked array of coupling lightguides. In anotherembodiment, the stacked array of coupling lightguides includes foldedcoupling lightguides and a non-folded coupling lightguide.

In another embodiment, the non-folded coupling lightguide is disposednear an edge of the lightguide. In one embodiment, the non-foldedcoupling lightguide is disposed in the middle region of the edge of thelightguide region. In a further embodiment, the non-folded couplinglightguide is disposed along a side of the lightguide region at a regionbetween the lateral sides of the lightguide region. In one embodiment,the non-folded coupling lightguide is disposed at various regions alongone edge of a lightguide region wherein a plurality of light inputcouplers are used to direct light into the side of a lightguide region.

In another embodiment, the folded coupling lightguides have lightcollimating edges, substantially linear edges, or light turning edges.In one embodiment, at least one selected from the group: array of foldedcoupling lightguides, light turning optical element, light collimatingoptical element, and light source are physically coupled to thenon-folded coupling lightguide. In another embodiment, folded couplinglightguides are physically coupled to each other and to the non-foldedcoupling lightguide by a pressure sensitive adhesive cladding layer andthe thickness of the unconstrained lightguide film including the lightemitting region and the array of coupling lightguides is less than oneof the following: 1.2 times, 1.5 times, 2 times, and 3 times thethickness of the array of coupling lightguides. By bonding the foldedcoupling lightguides only to themselves, the coupling lightguides (whenun-constrained) typically bend upward and increase the thickness of thearray due to the folded coupling lightguides not being physicallycoupled to a fixed or relatively constrained region. By physicallycoupling the folded coupling lightguides to a non-folded couplinglightguide, the array of coupling lightguides is physically coupled to aseparate region of the film which increases the stability and thusreduces the ability of the elastic energy stored from the bend to bereleased.

Coupling Lightguide Stack

In one embodiment, coupling lightguides extending from a lightguideregion in a film-based lightguide are folded at a 90 degree fold anglewith their ends stacked. In this embodiment, the radius of curvature foreach of the coupling lightguides is different due to the thickness ofeach of the coupling lightguides. In this embodiment, the radius ofcurvature for the nth coupling lightguide is determined by the equation:R _(n) =R ₁+(n−1)/2t,where R₁ is an initial (smallest radius) coupling lightguide radius, andt is a thickness of the coupling lightguides.

The coupling lightguide stack can be configured in numerous ways tocompensate for the different radii of curvature. In one embodiment, thecoupling lightguides have one or more compensation features selectedfrom the group: staggered light input surfaces; coupling lightguidesoriented at an angle with respect to each other; varying lateral foldlocations; coupling lightguides angled in an oriented stack; non-uniformtension or torsion; a constant fold radius of curvature stack; and othercompensation techniques or features.

Light Mixing Region

In one embodiment, a light emitting device includes a light mixingregion disposed in an optical path between the light input coupler andthe lightguide region. The light mixing region can provide a region forthe light output from individual coupling lightguides to mix togetherand improve at least one of a spatial luminance uniformity, a spatialcolor uniformity, an angular color uniformity, an angular luminanceuniformity, an angular luminous intensity uniformity or any combinationthereof within a region of the lightguide or of the surface or output ofthe light emitting region or light emitting device. In one embodiment, awidth of the light mixing region is selected from a range from 0.1 mm(for small displays) to more than 10 feet (for large billboards). In oneembodiment, the light mixing region is the region disposed along anoptical path near the end region of the coupling lightguides whereinlight from two or more coupling lightguides may inter-mix andsubsequently travel to a light emitting region of the lightguide. In oneembodiment, the light mixing region is formed from the same component ormaterial as at least one of the lightguide, lightguide region, lightinput coupler, and coupling lightguides.

Width of the Light Mixing Region or Array of Coupling Lightguides

In one embodiment, the length of the array of coupling lightguidesand/or the light mixing region is longer than the light emitting regionor lightguide region in a direction parallel to the array direction ofthe coupling lightguides (perpendicular to the extended direction of thearray of coupling lightguides). In one embodiment, the array of couplinglightguides and/or the light mixing region extends past a lateral sideof the light emitting region in the direction parallel to the arraydirection of the coupling lightguides (the perpendicular to the extendeddirection of the coupling lightguides) by a distance selected from thegroup: greater than 1 millimeter; greater than 2 millimeters; greaterthan 4 millimeters; greater than 6 millimeters; greater than 10millimeters; greater than 15 millimeters; greater than 20 millimeters;greater than 50% of the average width of the coupling lightguides;greater than 100% of the average width of the coupling lightguides; andgreater than 1%, 2%, 5%, or 10% of the length of the light emittingregion in the direction parallel to the array direction of the couplinglightguides. In one embodiment, the array of coupling lightguides orlight mixing region extends past the lateral edge of the light emittingregion opposite the direction of the fold. In a further embodiment, thearray of coupling lightguides or light mixing region extends past thelateral side of the light emitting region in the direction of the fold.In one embodiment, more light can be introduced into the edge region(defined as the region of the light emitting area within 10% of thelateral edge) by extending the array of coupling lightguides past thelateral edge of the light emitting region and/or extending the lightmixing region past the lateral edge of the light emitting region. In afurther embodiment, a lateral edge of the light mixing region, a lateraledge of one or more coupling lightguides, or an internal light directingedge is oriented at a first extended orientation angle to the extendeddirection of the coupling lightguides to direct light from the extendedregion of the array of coupling lightguides or the light mixing regiontoward the light emitting region of the film-based lightguide. In oneembodiment, the first extended orientation angle is greater than oneselected from the group: 0, 2, 5, 10, 20, 30, 45, and 60 degrees. Forexample, in one embodiment, the array of coupling lightguides includes acoupling lightguide that extends past the far lateral edge (the edgefurthest from the light source) of the light emitting area and the lightmixing region includes a lateral edge with an extended orientation angleof 30 degrees. In this embodiment, the far coupling lightguides arelonger in length, and thus more light is absorbed through the material.One method of compensation for the light flux difference reaching thefar edge region of the light emitting area due to the longer path lengthof light traveling toward the far edge region of the light emitting areais to add an additional coupling lightguide that can receive adistributed portion of the light from the light source and direct itinto the far edge region of the light emitting area by an angled lateraledge in the extended coupling lightguide, the light mixing region, or aninternal light directing edge.

Housing or Holding Device for Light Input Coupler

In one embodiment, a light emitting device includes a housing or holdingdevice that holds or includes at least part of a light input coupler andlight source. The housing or holding device may house or contain withinat least one selected from the group: light input coupler, light source,coupling lightguides, lightguide, optical components, electricalcomponents, heat sink or other thermal components, attachmentmechanisms, registration mechanisms, folding mechanisms devices, andframes. The housing or holding device may include a plurality ofcomponents or any combination of the aforementioned components. Thehousing or holding device may serve one or more of functions selectedfrom the group: protect from dust and debris contamination, provideair-tight seal, provide a water-tight seal, house or contain components,provide a safety housing for electrical or optical components, assistwith the folding or bending of the coupling lightguides, assist in thealignment or holding of the lightguide, coupling lightguide, lightsource or light input coupler relative to another component, maintainthe arrangement of the coupling lightguides, recycle light (such as withreflecting inner walls), provide attachment mechanisms for attaching thelight emitting device to an external object or surface, provide anopaque container such that stray light does not escape through specificregions, provide a translucent surface for displaying indicia orproviding illumination to an object external to the light emittingdevice, include a connector for release and interchangeability ofcomponents, and provide a latch or connector to connect with otherholding devices or housings.

In one embodiment, the housing or holding device includes at least oneselected from the group: connector, pin, clip, latch, adhesive region,clamp, joining mechanism, and other connecting element or mechanicalmeans to connect or hold the housing or holding device to anotherhousing or holding device, lightguide, coupling lightguide, film, strip,cartridge, removable component or components, an exterior surface suchas a window or automobile, light source, electronics or electricalcomponent, circuit board for the electronics or light source such as anLED, heat sink or other thermal control element, frame of the lightemitting device, and other component of the light emitting device.

In a another embodiment, the input ends and output ends of the couplinglightguides are held in physical contact with the relative positionmaintaining elements by at least one selected from the group: magneticgrips, mechanical grips, clamps, screws, mechanical adhesion, chemicaladhesion, dispersive adhesion, diffusive adhesion, electrostaticadhesion, vacuum holding, or an adhesive.

Curved or Flexible Housing

In another embodiment, the housing includes at least one curved surface.A curved surface can permit non-linear shapes or devices or facilitateincorporating non-planer or bent lightguides or coupling lightguides. Inone embodiment, a light emitting device includes a housing with at leastone curved surface wherein the housing includes curved or bent couplinglightguides. In another embodiment, the housing is flexible such that itmay be bent temporarily, permanently or semi-permanently. By using aflexible housing, for example, the light emitting device may be able tobe bent such that the light emitting surface is curved along with thehousing, the light emitting area may curve around a bend in a wall orcorner, for example. In one embodiment, the housing or lightguide may bebent temporarily such that the initial shape is substantially restored(bending a long housing to get it through a door for example). Inanother embodiment, the housing or lightguide may be bent permanently orsemi-permanently such that the bent shape is substantially sustainedafter release (such as when it is desired to have a curved lightemitting device to provide a curved sign or display, for example).

Housing Including a Thermal Transfer Element

In one embodiment, the housing includes a thermal transfer elementdisposed to transfer heat from a component within the housing to anouter surface of the housing. In another embodiment, the thermaltransfer element is one selected from the group: heat sink, metallic orceramic element, fan, heat pipe, synthetic jet, air jet producingactuator, active cooling element, passive cooling element, rear portionof a metal core or other conductive circuit board, thermally conductiveadhesive, or other component known to thermally conduct heat. In oneembodiment, the thermal transfer element has a thermal conductivity(W/(m·K)) greater than one selected from the group: 0.2, 0.5, 0.7, 1, 3,5, 50, 100, 120, 180, 237, 300, and 400. In another embodiment, a framesupporting the film-based lightguide (such as one that holds tension inthe film to maintain flatness) is a thermal transfer element. In oneembodiment, the light source is an LED and the LED is thermally coupledto the ballast or frame that is a thermal transfer element. In a furtherembodiment, a frame or ballast used to thermally transfer heat away fromthe light source and is also a housing for the light emitting device.

Low Contact Area Cover

In one embodiment, a low contact area cover is disposed between at leastone coupling lightguide and the exterior to the light emitting device.The low contact area cover or wrap provides a low surface area ofcontact with a region of the lightguide or a coupling lightguide and mayfurther provide at least one selected from the group: protection fromfingerprints, protection from dust or air contaminants, protection frommoisture, protection from internal or external objects that woulddecouple or absorb more light than the low contact area cover when incontact in one or more regions with one or more coupling lightguides,provide a means for holding or including at least one couplinglightguide, hold the relative position of one or more couplinglightguides, reflect light back through the lightguide, and prevent thecoupling lightguides from unfolding into a larger volume or contact witha surface that could de-couple or absorb light. In one embodiment, thelow contact area cover is disposed substantially around one or morecoupling lightguide stacks or arrays and provides one or more of thefunctions selected from the group: reducing the dust buildup on thecoupling lightguides, protecting one or more coupling lightguides fromfrustrated total internal reflection or absorption by contact withanother light transmitting or absorbing material, and preventing orlimiting scratches, cuts, dents, or deformities from physical contactwith other components or assemblers and/or users of the device.

Cladding Layer

In one embodiment, at least one of the light input coupler, couplinglightguide, light mixing region, lightguide region, and lightguideincludes a cladding layer optically coupled to at least one surface. Acladding region, as used herein, is a layer optically coupled to asurface wherein the cladding layer includes a material with a refractiveindex, n_(clad), less than the refractive index of the material, n_(m),of the surface to which it is optically coupled. In a one embodiment,the average thickness of one or both cladding layers of the lightguideis less than one selected from the group: 100 microns, 60 microns, 30microns, 20 microns, 10 microns, 6 microns, 4 microns, 2 microns, 1micron, 0.8 microns, 0.5 microns, 0.3 microns, and 0.1 microns. In oneembodiment, the cladding layer includes an adhesive such as asilicone-based adhesive, acrylate-based adhesive, epoxy, radiationcurable adhesive, UV curable adhesive, or other light transmittingadhesive. Fluoropolymer materials may be used as a low refractive indexcladding material. In one embodiment, the cladding region is opticallycoupled to one or more of the following: a lightguide, a lightguideregion, a light mixing region, one surface of the lightguide, twosurfaces of the lightguide, a light input coupler, coupling lightguides,and an outer surface of the film. In another embodiment, the cladding isdisposed in optical contact with the lightguide, the lightguide region,or a layer or layers optically coupled to the lightguide and thecladding material is not disposed on one or more coupling lightguides.

In one embodiment, the cladding is one selected from the group: methylbased silicone pressure sensitive adhesive, fluoropolymer material(applied using a coating including a fluoropolymer substantiallydissolved in a solvent), and a fluoropolymer film. The cladding layermay be incorporated to provide a separation layer between the core orcore part of a lightguide region and the outer surface to reduceundesirable out-coupling (for example, frustrated totally internallyreflected light by touching the film with an oily finger) from the coreor core region of a lightguide. Components or objects such as additionalfilms, layers, objects, fingers, dust etc. that come in contact oroptical contact directly with a core or core region of a lightguide maycouple light out of the lightguide, absorb light or transfer the totallyinternally reflected light into a new layer. By adding a cladding layerwith a lower refractive index than the core, a portion of the light willtotally internally reflect at the core-cladding layer interface.Cladding layers may also be used to provide the benefit of at least oneof increased rigidity, increased flexural modulus, increased impactresistance, anti-glare properties, provide an intermediate layer forcombining with other layers such as in the case of a claddingfunctioning as a tie layer or a base or substrate for an anti-reflectioncoating, a substrate for an optical component such as a polarizer,liquid crystal material, increased scratch resistance, provideadditional functionality (such as a low-tack adhesive to bond thelightguide region to another element, a window “cling type” film such asa highly plasticized PVC). The cladding layer may be an adhesive, suchas a low refractive index silicone adhesive which is optically coupledto another element of the device, the lightguide, the lightguide region,the light mixing region, the light input coupler, or a combination ofone or more of the aforementioned elements or regions. In oneembodiment, a cladding layer is optically coupled to a rear polarizer ina backlit liquid crystal display. In another embodiment, the claddinglayer is optically coupled to a polarizer or outer surface of afront-lit display such as an electrophoretic display, e-book display,e-reader display, MEMs type display, electronic paper displays such asE-Ink® display by E Ink Corporation, reflective or partially reflectiveLCD display, cholesteric display, or other display capable of beingilluminated from the front. In another embodiment, the cladding layer isan adhesive that bonds the lightguide or lightguide region to acomponent such as a substrate (glass or polymer), optical element (suchas a polarizer, retarder film, diffuser film, brightness enhancementfilm, protective film (such as a protective polycarbonate film), thelight input coupler, coupling lightguides, or other element of the lightemitting device. In one embodiment, the cladding layer is separated fromthe lightguide or lightguide region core layer by at least oneadditional layer or adhesive.

In one embodiment, the cladding region is optically coupled to one ormore surfaces of the light mixing region to prevent out-coupling oflight from the lightguide when it is in contact with another component.In this embodiment, the cladding also enables the cladding and lightmixing region to be physically coupled to another component.

Cladding Location

In one embodiment, the cladding region is optically coupled to at leastone selected from the group: lightguide, lightguide region, light mixingregion, one surface of the lightguide, two surfaces of the lightguide,light input coupler, coupling lightguides, and an outer surface of thefilm. In another embodiment, the cladding is disposed in optical contactwith the lightguide, lightguide region, or layer or layers opticallycoupled to the lightguide and the cladding material is not disposed onone or more coupling lightguides. In one embodiment, the couplinglightguides do not include a cladding layer between the core regions inthe region near the light input surface or light source. In anotherembodiment, the core regions may be pressed or held together and theedges may be cut and/or polished after stacking or assembly to form alight input surface or a light turning edge that is flat, curved, or acombination thereof. In another embodiment, the cladding layer is apressure sensitive adhesive and the release liner for the pressuresensitive adhesive is selectively removed in the region of one or morecoupling lightguides that are stacked or aligned together into an arraysuch that the cladding helps maintain the relative position of thecoupling lightguides relative to each other. In another embodiment, theprotective liner is removed from the inner cladding regions of thecoupling lightguides and is left on one or both outer surfaces of theouter coupling lightguides.

Lightguide Configuration and Properties

In one embodiment, the thickness of the film, lightguide and/orlightguide region is within a range of 0.005 mm to 0.5 mm. In anotherembodiment, the thickness of the film or lightguide is within a range of0.025 mm (0.001 inches) to 0.5 mm (0.02 inches). In a furtherembodiment, the thickness of the film, lightguide and/or lightguideregion is within a range of 0.050 mm to 0.175 mm. In one embodiment, thethickness of the film, lightguide or lightguide region is less than 0.2mm or less than 0.5 mm. In one embodiment, one or more of a thickness, alargest thickness, an average thickness, a greater than 90% of theentire thickness of the film, a lightguide, and a lightguide region isless than 0.2 millimeters.

Optical Properties of the Lightguide or Light Transmitting Material

With regards to the optical properties of lightguides or lighttransmitting materials for certain embodiments, the optical propertiesspecified herein may be general properties of the lightguide, the core,the cladding, or a combination thereof or they may correspond to aspecific region (such as a light emitting region, light mixing region,or light extracting region), surface (light input surface, diffusesurface, flat surface), and direction (such as measured normal to thesurface or measured in the direction of light travel through thelightguide).

Refractive Index of the Light Transmitting Material

In one embodiment, the core material of the lightguide has a higherrefractive index than the cladding material. In one embodiment, the coreis formed from a material with a refractive index (n_(D)) greater thanone selected from the group: 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, and 3.0. In anotherembodiment, the refractive index (n_(D)) of the cladding material isless than one selected from the group: 1.1, 1.2, 1.3, 1.4, 1.5, 1.6,1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, and 2.5.

Edges of the Lightguide

In one embodiment, the edges of the lightguide or lightguide region arecoated, bonded to or disposed adjacent to a specularly reflectingmaterial, partially diffusely reflecting material, or diffuse reflectingmaterial. In one embodiment, the lightguide edges are coated with aspecularly reflecting ink including nano-sized or micron-sized particlesor flakes which reflect the light substantially specularly. In anotherembodiment, a light reflecting element (such as a specularly reflectingmulti-layer polymer film with high reflectivity) is disposed near thelightguide edge and is disposed to receive light from the edge andreflect it and direct it back into the lightguide. In anotherembodiment, the lightguide edges are rounded and the percentage of lightdiffracted from the edge is reduced. One method of achieving roundededges is by using a laser to cut the lightguide from a film and achieveedge rounding through control of the processing parameters (speed ofcut, frequency of cut, laser power, etc.). In another embodiment, theedges of the lightguide are tapered, angled serrated, or otherwise cutor formed such that light from a light source propagating within thecoupling lightguide reflects from the edge such that it is directed intoan angle closer to the optical axis of the light source, toward a foldedregion, toward a bent region, toward a lightguide, toward a lightguideregion, or toward the optical axis of the light emitting device. In afurther embodiment, two or more light sources are disposed to eachcouple light into two or more coupling lightguides including lightre-directing regions for each of the two or more light sources thatinclude first and second reflective surfaces which direct a portion oflight from the light source into an angle closer to the optical axis ofthe light source, toward a folded or bent region, toward a lightguideregion, toward a lightguide region, or toward the optical axis of thelight emitting device. In one embodiment, one or more edges of thecoupling lightguides, the lightguide, the light mixing region, or thelightguide region include a curve or arcuate profile in the region ofintersection between two or more surfaces of the film in a region.

Shape of the Lightguide

In one embodiment, at least a portion of the lightguide shape orlightguide surface is substantially planar, curved, cylindrical, aformed shape from a substantially planar film, spherical, partiallyspherical, angled, twisted, rounded, have a quadric surface, spheroid,cuboid, parallelepiped, triangular prism, rectangular prism, ellipsoid,ovoid, cone pyramid, tapered triangular prism, wave-like shape, and/orother known suitable geometrical solids or shapes. In one embodiment,the lightguide is a film formed into a shape by thermoforming or othersuitable forming techniques. In another embodiment, the film or regionof the film is tapered in at least one direction. In a furtherembodiment, a light emitting device includes a plurality of lightguidesand a plurality of light sources physically coupled or arranged together(such as tiled in a 1×2 array for example). In another embodiment, thesurface of the lightguide region of the film is substantially in theshape of a polygon, triangle, rectangle, square, trapezoid, diamond,ellipse, circle, semicircle, segment or sector of a circle, crescent,oval, annulus, alphanumeric character shaped (such as “U-shaped” or“T-shaped), or a combination of one or more of the aforementionedshapes. In another embodiment, the shape of the lightguide region of thefilm is substantially in the shape of a polyhedron, toroidal polyhedron,curved polyhedron, spherical polyhedron, rectangular cuboid, cuboid,cube, orthotope, stellation, prism, pyramid, cylinder, cone, truncatedcone, ellipsoid, paraboloid, hyperboloid, sphere, or a combination ofone or more of the aforementioned shapes.

Lightguide Material

In one embodiment, a light emitting device includes a lightguide orlightguide region formed from at least one light transmitting material.In one embodiment, the lightguide is a film includes at least one coreregion and at least one cladding region, each including at least onelight transmitting material. In one embodiment, the light transmittingmaterial is a thermoplastic, thermoset, rubber, polymer, hightransmission silicone, glass, composite, alloy, blend, silicone, orother suitable light transmitting material, or a combination thereof. Inone embodiment, a component or region of the light emitting deviceincludes a suitable light transmitting material, such as one or more ofthe following: cellulose derivatives (e.g., cellulose ethers such asethylcellulose and cyanoethylcellulose, cellulose esters such ascellulose acetate), acrylic resins, styrenic resins (e.g., polystyrene),polyvinyl-series resins [e.g., poly(vinyl ester) such as poly(vinylacetate), poly(vinyl halide) such as poly(vinyl chloride), polyvinylalkyl ethers or polyether-series resins such as poly(vinyl methylether), poly(vinyl isobutyl ether) and poly(vinyl t-butyl ether)],polycarbonate-series resins (e.g., aromatic polycarbonates such asbisphenol A-type polycarbonate), polyester-series resins (e.g.,homopolyesters, for example, polyalkylene terephthalates such aspolyethylene terephthalate and polybutylene terephthalate, polyalkylenenaphthalates corresponding to the polyalkylene terephthalates;copolyesters including an alkylene terephthalate and/or alkylenenaphthalate as a main component; homopolymers of lactones such aspolycaprolactone), polyamide-series resin (e.g., nylon 6, nylon 66,nylon 610), urethane-series resins (e.g., thermoplastic polyurethaneresins), copolymers of monomers forming the above resins [e.g., styreniccopolymers such as methyl methacrylate-styrene copolymer (MS resin),acrylonitrile-styrene copolymer (AS resin), styrene-(meth)acrylic acidcopolymer, styrene-maleic anhydride copolymer and styrene-butadienecopolymer, vinyl acetate-vinyl chloride copolymer, vinyl alkylether-maleic anhydride copolymer]. Incidentally, the copolymer may bewhichever of a random copolymer, a block copolymer, or a graftcopolymer.

Lightguide Material with Adhesive Properties

In another embodiment, the lightguide includes a material with at leastone selected from the group: chemical adhesion, dispersive adhesion,electrostatic adhesion, diffusive adhesion, and mechanical adhesion toat least one element of the light emitting device (such as a carrierfilm with a coating, an optical film, the rear polarizer in an LCD, abrightness enhancing film, another region of the lightguide, a couplinglightguide, a thermal transfer element such as a thin sheet includingaluminum, or a white reflector film). In a further embodiment, at leastone of the core material or cladding material of the lightguide is anadhesive material. In a further embodiment, at least one selected fromthe group: core material, cladding material, and a material disposed ona cladding material of the lightguide is at least one selected from thegroup: a pressure sensitive adhesive, a contact adhesive, a hotadhesive, a drying adhesive, a multi-part reactive adhesive, a one-partreactive adhesive, a natural adhesive, and a synthetic adhesive. In afurther embodiment, the first core material of a first couplinglightguide is adhered to the second core material of a second couplinglightguide due to the adhesion properties of the first core material,second core material, or a combination thereof. In another embodiment,the cladding material of a first coupling lightguide is adhered to thecore material of a second coupling lightguide due to the adhesionproperties of the cladding material. In another embodiment, the firstcladding material of a first coupling lightguide is adhered to thesecond cladding material of a second coupling lightguide due to theadhesion properties of the first cladding material, second claddingmaterial, or a combination thereof. In one embodiment, the core layer isan adhesive and is coated onto at least one selected from the group:cladding layer, removable support layer, protective film, secondadhesive layer, polymer film, metal film, second core layer, low contactarea cover, and planarization layer. In another embodiment, the claddingmaterial or core material has adhesive properties and has an ASTM D3330Peel strength greater than one selected from the group: 8.929, 17.858,35.716, 53.574, 71.432, 89.29, 107.148, 125.006, 142.864, 160.722,178.580 kilograms per meter of bond width when adhered to an element ofthe light emitting device, such as for example without limitation, acladding layer, a core layer, a low contact area cover, a circuit board,or a housing.

In another embodiment, a tie layer, primer, or coating is used topromote adhesion between at least one selected from the group: corematerial and cladding material, lightguide and housing, core materialand element of the light emitting device, cladding material and elementof the light emitting device. In one embodiment, the tie layer orcoating includes a dimethyl silicone or variant thereof and a solvent.In another embodiment, the tie layer includes a phenyl based primer suchas those used to bridge phenylsiloxane-based silicones with substratematerials. In another embodiment, the tie layer includes aplatinum-catalyzed, addition-cure silicone primer such as those used tobond plastic film substrates and silicone pressure sensitive adhesives.

In a further embodiment, at least one region of the core material orcladding material has adhesive properties and is optical coupled to asecond region of the core or cladding material such that the ASTM D1003luminous transmittance through the interface is at least one selectedfrom the group: 1%, 2%, 3%, and 4% greater than the transmission throughthe same two material at the same region with an air gap disposedbetween them.

In one embodiment, the core material of the lightguide includes amaterial with a critical surface tension less than one selected from thegroup: 33, 32, 30, 27, 25, 24 and 20 mN/m. In another embodiment, thecore material has a critical surface tension less than one selected fromthe group: 33, 30, 27, 25, 24 and 20 mN/m and is surface treated toincrease the critical surface tension to greater than one selected fromthe group: 27, 30, 33, 35, 37, 40, and 50. In one embodiment, thesurface treatment includes exposing the surface to at least one selectedfrom the group: a plasma, a flame, and a tie layer material. In oneembodiment, the surface tension of the core material of the lightguideis reduced to reduce light extraction from a surface in contact due to“wet-out” and optical coupling. In another embodiment, the surfacetension of the surface of the lightguide

Multilayer Lightguide

In one embodiment, the lightguide includes at least two layers orcoatings. In another embodiment, the layers or coatings function as atleast one selected from the group: a core layer, a cladding layer, a tielayer (to promote adhesion between two other layers), a layer toincrease flexural strength, a layer to increase the impact strength(such as Izod, Charpy, Gardner, for example), and a carrier layer. In afurther embodiment, at least one layer or coating includes amicrostructure, surface relief pattern, light extraction features,lenses, or other non-flat surface features which redirect a portion ofincident light from within the lightguide to an angle whereupon itescapes the lightguide in the region near the feature. For example, thecarrier film may be a silicone film with embossed light extractionfeatures disposed to receive a thermoset polycarbonate resin core regionincluding a thermoset material

In one embodiment, a thermoset material is coated onto a thermoplasticfilm wherein the thermoset material is the core material and thecladding material is the thermoplastic film or material. In anotherembodiment, a first thermoset material is coated onto a film including asecond thermoset material wherein the first thermoset material is thecore material and the cladding material is the second thermoset plastic.

Light Extraction Method

In one embodiment, one or more of the lightguide, the lightguide region,and the light emitting region includes at least one light extractionfeature or region. In one embodiment, the light extraction region may bea raised or recessed surface pattern or a volumetric region. Raised andrecessed surface patterns include, without limitation, scatteringmaterial, raised lenses, scattering surfaces, pits, grooves, surfacemodulations, microlenses, lenses, diffractive surface features,holographic surface features, photonic bandgap features, wavelengthconversion materials, holes, edges of layers (such as regions where thecladding is removed from covering the core layer), pyramid shapes, prismshapes, and other geometrical shapes with flat surfaces, curvedsurfaces, random surfaces, quasi-random surfaces, and combinationsthereof. The volumetric scattering regions within the light extractionregion may include dispersed phase domains, voids, absence of othermaterials or regions (gaps, holes), air gaps, boundaries between layersand regions, and other refractive index discontinuities orinhomogeneities within the volume of the material different thatco-planar layers with parallel interfacial surfaces.

In one embodiment, the light extraction feature is substantiallydirectional and includes one or more of the following: an angled surfacefeature, a curved surface feature, a rough surface feature, a randomsurface feature, an asymmetric surface feature, a scribed surfacefeature, a cut surface feature, a non-planar surface feature, a stampedsurface feature, a molded surface feature, a compression molded surfacefeature, a thermoformed surface feature, a milled surface feature, anextruded mixture, a blended materials, an alloy of materials, acomposite of symmetric or asymmetrically shaped materials, a laserablated surface feature, an embossed surface feature, a coated surfacefeature, an injection molded surface feature, an extruded surfacefeature, and one of the aforementioned features disposed in the volumeof the lightguide. For example, in one embodiment, the directional lightextraction feature is a 100 micron long, 45 degree angled facet grooveformed by UV cured embossing a coating on the lightguide film thatsubstantially directs a portion of the incident light within thelightguide toward 0 degrees from the surface normal of the lightguide.

In one embodiment, the light extraction feature is a specularly,diffusive, or a combination thereof reflective material. For example,the light extraction feature may be a substantially specularlyreflecting ink disposed at an angle (such as coated onto a groove) orthe light extraction feature may be a substantially diffusely reflectiveink such as an ink including titanium dioxide particles within amethacrylate-based binder.

Multiple Lightguides

In one embodiment, a light emitting device includes more than onelightguide to provide one or more of the following: color sequentialdisplay, localized dimming backlight, red, green, and blue lightguides,animation effects, multiple messages of different colors, NVIS anddaylight mode backlight (one lightguide for NVIS, one lightguide fordaylight for example), tiled lightguides or backlights, and large arealight emitting devices including smaller light emitting devices. Inanother embodiment, a light emitting device includes a plurality oflightguides optically coupled to each other. In another embodiment, atleast one lightguide or a component thereof includes a region withanti-blocking features such that the lightguides do not substantiallycouple light directly into each other due to touching.

Multiple Lightguides to Provide Pixelated Color

In one embodiment, a light emitting device includes a first lightguideand second lightguide disposed to receive light from a first and secondlight source, respectively, through two different optical paths whereinthe first and second light source emit light of different colors and thelight emitting regions of the first and second lightguides includepixelated regions spatially separated in the plane including the lightoutput plane of the light emitting device at the pixelated regions (forexample, separated in the thickness direction of the film-basedlightguides).

Lightguide Folding Around Components

In one embodiment, at least one selected from the group: lightguide,lightguide region, light mixing region, plurality of lightguides,coupling lightguides, and light input coupler bends or folds such thatthe component other components of the light emitting device are hiddenfrom view, located behind another component or the light emittingregion, or are partially or fully enclosed. These components aroundwhich they may bend or fold include components of the light emittingdevice such as light source, electronics, driver, circuit board, thermaltransfer element, spatial light modulator, display, housing, holder, orother components such that the components are disposed behind the foldedor bent lightguide or other region or component. In one embodiment, afrontlight for a reflective display includes a lightguide, couplinglightguides and a light source wherein one or more regions of thelightguide are folded and the light source is disposed substantiallybehind the display. In one embodiment, the light mixing region includesa fold and the light source and/or coupling lightguides aresubstantially disposed on the side of the film-based lightguide oppositethe light emitting region of the device or reflective display. In oneembodiment, a reflective display includes a lightguide that is foldedsuch that a region of the lightguide is disposed behind the reflectivespatial light modulator of the reflective display. In one embodiment,the fold angle is between 150 and 210 degrees in one plane. In anotherembodiment, the fold angle is substantially 180 degrees in one plane. Inone embodiment, the fold is substantially 150 and 210 degrees in a planeparallel to the optical axis of the light propagating in the film-basedlightguide. In one embodiment, more than one input coupler or componentis folded behind or around the lightguide, light mixing region or lightemitting region. In this embodiment, for example, two light inputcouplers from opposite sides of the light emitting region of the samefilm may be disposed adjacent each other or utilize a common lightsource and be folded behind the spatial light modulator of a display. Inanother embodiment, tiled light emitting devices include light inputcouplers folded behind and adjacent or physically coupled to each otherusing the same or different light sources. In one embodiment, the lightsource or light emitting area of the light source is disposed within thevolume bounded by the edge of the light emitting region and the normalto the light emitting region on the side of the lightguide opposite theviewing side. In another embodiment, at least one of the light source,light input coupler, coupling lightguides, or region of the light mixingregion is disposed behind the light emitting region (on the side of thelightguide opposite the viewing side) or within the volume bounded bythe edge of the light emitting region and the normal to the lightemitting region on the side of the lightguide opposite the viewing side.

In another embodiment, the lightguide region, light mixing region, orbody of the lightguide extends across at least a portion of the array ofcoupling lightguides or a light emitting device component. In anotherembodiment, the lightguide region, light mixing region, or body of thelightguide extends across a first side of the array of couplinglightguides or a first side of the light emitting device component. In afurther embodiment, the lightguide region, light mixing region or bodyof the lightguide extends across a first side and a second side of thearray of coupling lightguides. For example, in one embodiment, the bodyof a film-based lightguide extends across two sides of a stack ofcoupling lightguides with a substantially rectangular cross section. Inone embodiment, the stacked array of coupling lightguides is oriented ina first orientation direction substantially parallel to their stackedsurfaces toward the direction of light propagation within the couplinglightguides, and the light emitting region is oriented in a seconddirection parallel to the optical axis of light propagating within thelight emitting region where the orientation difference angle is theangular difference between the first orientation direction and thesecond orientation direction. In one embodiment, the orientationdifference angle is selected from the group: 0 degrees, greater than 0degrees, greater than 0 degrees and less than 90 degrees, between 70degrees and 110 degrees, between 80 degrees and 100 degrees, greaterthan 0 degrees and less than 180 degrees, between 160 degrees and 200degrees, between 170 degrees and 190 degrees, and greater than 0 degreesand less than 360 degrees.

In one embodiment, at least one selected from the group: lightguide,lightguide region, light mixing region, plurality of lightguides,coupling lightguides, and light input coupler bends or folds such thatit wraps around a component of the light emitting device more than once.For example, in one embodiment, a lightguide wraps around the couplinglightguides two times, three times, four times, five times, or more thanfive times. In another embodiment, the lightguide, lightguide region,light mixing region, plurality of lightguides, coupling lightguides, orlight input coupler may bend or fold such that it wraps completelyaround a component of the light emitting device and partially wrapsagain around. For example, a lightguide may wrap around a relativeposition maintaining element 1.5 times (one time around and half wayaround again). In another embodiment, the lightguide region, lightmixing region or body of the lightguide further extends across a third,fourth, fifth, or sixth side of the array of coupling lightguides orlight emitting device component. For example, in one embodiment, thelight mixing region of a film-based lightguide extends completely aroundfour sides of the relative position maintaining element plus across aside again (fifth side). In another example, the light mixing regionwraps around a stack of coupling lightguides and relative positionmaintaining element more than three times.

In one embodiment, wrapping the lightguide, lightguide region, lightmixing region, plurality of lightguides, coupling lightguides, or lightinput coupler around a component provides a compact method for extendingthe length of a region of the lightguide. For example, in oneembodiment, the light mixing region is wrapped around the stack ofcoupling lightguides to increase the light mixing distance within thelight mixing region such that the spatial color or the light fluxuniformity of the light entering the light emitting region is improved.

In one embodiment, the wrapped or extended region of the lightguide isoperatively coupled to the stack of coupling lightguides or a componentof the light emitting device. In one embodiment, the wrapped or extendedregion of the lightguide is held with adhesive to the stack of couplinglightguides or the component of the light emitting device. For example,in one embodiment, the light mixing region includes a pressure sensitiveadhesive cladding layer that extends or wraps and adheres to one or moresurfaces of one or more coupling lightguides or to the component of thelight emitting device. In another embodiment, the light mixing regionincludes a pressure sensitive adhesive layer that adheres to at leastone surface of a relative position maintaining element. In anotherembodiment, a portion of the film-based lightguide includes a layer thatextends or wraps to one or more surfaces of one or more couplinglightguides or a component of the light emitting device. In anotherembodiment, the wrapped or extended region of the lightguide extendsacross one or more surfaces or sides, or wraps around one or more lightsources. The wrapping or extending of a lightguide or lightguide regionacross one or more sides or surfaces of the stack of couplinglightguides or the component of the light emitting device, may occur byphysically translating or rotating the lightguide or the lightguideregion, or may occur by rotating the stack of coupling lightguides orthe component. Thus, the physical configuration does not require aparticular method of achieving the wrapping or extending.

Multiple Bends in the Lightguide

In one embodiment, a film-based lightguide includes two bends in thefilm. In another embodiment, the two bends in the film-based lightguideare within the same plane and in the light mixing region of the film.For example, in one embodiment, a film-based lightguide operativelycoupled to the top of a frame includes a first bend to fold a lightmixing region behind the frame to position at least one of a lightsource, a light input coupler, and a relative position maintainingelement behind the light emitting region of the lightguide. In thisembodiment, the lightguide includes a second bend that positions atleast one of the light source, light input coupler, and relativeposition maintaining element at a distance from the light emittingregion of the lightguide in the thickness direction less than thediameter of the first bend. In this embodiment, the second bend canbring the component(s) closer to the light emitting region than thesingle bend for long light mixing regions. Similarly, a large first bend(such as a first bend with a first bend angle greater than 180 degrees)can position at least one of a light source, light input coupler, andrelative position maintaining element closer to the light emittingregion and behind the light emitting region of the lightguide. In oneembodiment, a method of manufacturing a light emitting device includesbending a film-based lightguide at a first bend with a first benddiameter such that a portion of the light mixing region is disposedbehind the light emitting region of the lightguide and the distancebetween the light emitting region of the lightguide and the portion ofthe light mixing region behind the light emitting region is less thanthe first bend diameter. In another embodiment, a method ofmanufacturing a light emitting device includes bending a film-basedlightguide at a first bend with a first bend diameter that positions afirst portion of the light mixing region behind the light emittingregion of the lightguide, and bending the lightguide at a second bendthat positions a second portion of the light mixing region of thelightguide such that the distance between the light emitting region ofthe lightguide and the second portion of the light mixing region behindthe light emitting region is less than the first bend diameter of thefirst bend.

In another embodiment, the lightguide further includes a planar regionbetween the second bend and at least one of the light source, the lightinput coupler, and the relative position maintaining element. Forexample, in one embodiment, the length of the light mixing region of afilm based lightguide is greater than 50% of the length of the lightemitting region and the lightguide includes a first bend to position thelight source and the light mixing region of the lightguide behind thelight emitting region. The volume of the device can be reduced byincluding a second bend in the lightguide that brings the light mixingregion closer to the light emitting region. In this embodiment, thelightguide can be operatively coupled to a frame on the top and bottomsurfaces of the frame and the diameter of the first bend (or the maximumseparation between the inner surfaces of the film) is greater than theaverage separation between the lower surface of the light emittingregion of the lightguide and the upper surface of the light mixingregion positioned underneath the light emitting region. In anotherembodiment, the light source and/or at least one coupling lightguide ispositioned at a distance from the light emitting region of thelightguide less than the diameter of the first bend or the maximumseparation between the inner surfaces of the film. In anotherembodiment, shape of the lightguide further includes an inflection pointin a plane including the first bend. In one embodiment, the lightguideextends from the relative position maintaining element (or the housingcomprising the relative position maintaining element) at the top side orthe bottom side wherein the top side of the relative positionmaintaining element is closer to the light mixing region when thelightguide is folded such that the relative position maintaining elementis below the light emitting region of the lightguide.

In another embodiment, the tapered edge of the tapered light mixingregion has an extended direction length, L_(t), and a displacement,D_(t), from the lateral edge of the lightguide in the light emittingregion. In one embodiment, L_(t)/D_(t) is greater than or equal to oneselected from the group: 0.2, 0.5, 1, 2, 3, 4, 5, 8, 10, and 20. Inanother embodiment, D_(t) is greater than one selected from the group:2, 4, 6, 8, 10, 20, 50, 75, 100, and 200 millimeters. In a furtherembodiment, L_(t) is greater than one selected from the group: 2, 4, 6,8, 10, 20, 50, 75, 100, and 200 millimeters. In another embodiment,L_(t) is greater than the thickness of a light collimating opticalelement parallel to its optical axis positioned to receive light fromthe light source and direct it toward the input surface of couplinglightguides extended from the film-based lightguide with a tapered lightmixing region. In a further embodiment, L_(t) is greater than thethickness of a light source plus the thickness of the light collimatingoptical element parallel to the optical axis of the light collimatingoptical element positioned to receive light from the light source anddirect it toward the input surface of coupling lightguides extended fromthe film-based lightguide with the tapered light mixing region. In oneembodiment the length of the light mixing region of the lightguide islarger than the length of the light emitting region and the light sourceand/or the coupling lightguides do not extend past the light emittingarea of the lightguide in the length direction.

In another embodiment, the lightguide further includes a third bend inthe same plane as the first bend and the second bend. In thisembodiment, the light mixing region of the film based lightguide can befolded behind the light emitting region, bent closer to the lightemitting region and be folded again onto itself to accommodate a longlight mixing region. In one embodiment, the lightguide includes one ormore bends or folds wherein each bend may positions the lightguidecloser to another region of the lightguide and/or fold one region of thelightguide upon (or behind or above) another region of the lightguide.In one embodiment, the diameter of the bend that folds the first regionof the lightguide behind the second region of the lightguide is the sameas or greater than the average distance of the second region to thefirst region beneath, behind, or above the light emitting region of thelightguide. In one embodiment, the light mixing region of the lightguideincludes the first region of the lightguide and the second region of thelightguide on opposite sides of the fold in the lightguide. In oneembodiment, the first region of the lightguide is the light emittingregion and the light mixing region includes the second region on theopposite side of the fold as the first region. In one embodiment, theratio of the length of the light mixing region to the length of thelight emitting region is greater than one selected from the group: 0.1,0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 3, and 4.

In one embodiment, one or more bends of a lightguide has a bend angle,the average angle formed between two substantially planar regions onboth sides of a bend or the angle proceeding or following an inflectionpoint in the lightguide, selected from the group: greater than 5,greater than 10, 20-70, 30-50, 45, 60-120, 70-110, 80-100, 90, 115-155,120-150, 135, 150-210, 160-200, 170-190, 175-185, 180, greater than 180,195-255, 205-245, 215-235, 220-230, 225, 240-300, 250-290, 260-250,265-275, 270, 285-345, 295-335, 305-325, 310-320, 315, 330-390, 340-380,350-370, 355-365, 360, and greater than 0 and less than 360 degrees. Forexample, in one embodiment, a lightguide includes a first bend with afirst bend angle of 180 degrees that bends the lightguide back underitself, and a second bend with a bend angle of 45 degrees that bends thelightguide closer to the light emitting region of the lightguide beforethe first bend. The lightguide in this example, could further include athird bend with a bend angle of 45 degrees that bends the light mixingregion of the lightguide back to parallel to (and beneath) the lightemitting region.

Light Absorbing Region or Layer

In one embodiment, one or more of the cladding, the adhesive, the layerdisposed between the lightguide and lightguide region and the outerlight emitting surface of the light emitting device, a patterned region,a printed region, and an extruded region on one or more surfaces orwithin a volume of the film includes a light absorbing material whichabsorbs a first portion of light in a first predetermined wavelengthrange.

Adhesion Properties of the Lightguide, Film, Cladding or Other Layer

In one embodiment, one or more of the lightguide, the core material, thelight transmitting film, the cladding material, and a layer disposed incontact with a layer of the film has adhesive properties or includes amaterial with one or more of the following: chemical adhesion,dispersive adhesion, electrostatic adhesion, diffusive adhesion, andmechanical adhesion to at least one element of the light emitting device(such as a carrier film with a coating, an optical film, the rearpolarizer in an LCD, a brightness enhancing film, another region of thelightguide, a coupling lightguide, a thermal transfer element such as athin sheet including aluminum, or a white reflector film) or an elementexternal to the light emitting device such as a window, wall, orceiling.

Light Redirecting Element Disposed to Redirect Light from the Lightguide

In one embodiment, a light emitting device includes a lightguide withlight redirecting elements disposed on or within the lightguide andlight extraction features disposed in a predetermined relationshiprelative to one or more light redirecting elements. In anotherembodiment, a first portion of the light redirecting elements aredisposed above a light extraction feature in a direction substantiallyperpendicular to the light emitting surface, lightguide, or lightguideregion.

Light Redirecting Element

As used herein, the light redirecting element is an optical elementwhich redirects a portion of light of a first wavelength range incidentin a first angular range into a second angular range different than thefirst. In one embodiment, the light redirecting element includes atleast one element selected from the group: refractive features, totallyinternally reflected feature, reflective surface, prismatic surface,microlens surface, diffractive feature, holographic feature, diffractiongrating, surface feature, volumetric feature, and lens. In a furtherembodiment, the light redirecting element includes a plurality of theaforementioned elements. The plurality of elements may be in the form ofa 2-D array (such as a grid of microlenses or close-packed array ofmicrolenses), a one-dimensional array (such as a lenticular lens array),random arrangement, predetermined non-regular spacing, semi-randomarrangement, or other predetermined arrangement. The elements mayinclude different features, with different surface or volumetricfeatures or interfaces and may be disposed at different thicknesseswithin the volume of the light redirecting element, lightguide, orlightguide region. The individual elements may vary in the x, y, or zdirection by at least one selected from the group: height, width,thickness, position, angle, radius of curvature, pitch, orientation,spacing, cross-sectional profile, and location in the x, y, or z axis.

Location of the Film-Based Lightguide

In one embodiment, the core region of the film-based lightguide ispositioned between two layers selected from the group: hardcoatingsubstrate, layer, or adhesive; anti-glare layer or anti-reflectionlayer, substrate or adhesive; color filter material, layer, substrate,or adhesive; first cladding of the lightguide; second cladding of thelightguide; cladding substrate or adhesive; film-based lightguideadhesive; electro-optic layer (such as liquid crystal layer orelectrophoretic layer, for example); viewer side substrate for theelectro-optic layer; substrate for the electro-optic layer on non-viewerside; adhesive or substrate for the electro-optic layer; reflectivematerial, film, layer, or substrate or adhesive for reflective layer;polarizer layer substrate, or adhesive for polarizer; light redirectinglayer; light extraction feature film; impact protection layer; internalcoating; conformal coating; circuit board; flexible connector; thermallyconducting film, layer (such as a stainless steel, copper, or aluminumfoil layer), substrate, or adhesive; sealant layer, film substrate oradhesive; air gap layer; spacer layer or substrate for the spacer layer;electrically conducting layer (transparent or opaque), substrate, oradhesive; anode layer, substrate, or adhesive for anode layer; cathodelayer, substrate or adhesive for cathode layer; active matrix layer,substrate or adhesive for active matrix layer; passive matrix layer,substrate or adhesive for passive matrix layer; and touchscreen layer,substrate for touchscreen, or adhesive for touchscreen layer. In anotherembodiment, the film-based lightguide functions as one or more of theaforementioned layers in addition to propagating light in a waveguidecondition.

In one embodiment, the film based lightguide is positioned between thecolor filter layer and the electro-optical layer such that the parallaxeffects due to high angle light are minimized (thus resulting in highercontrast, greater resolution, or increased brightness). In anotherembodiment, the film-based lightguide is the substrate for the colorfilter material or layer. In another embodiment, the film-basedlightguide is the substrate for the electro-optic material or layer.

In one embodiment, the distance between the light extraction featuresand the color filters in a multi-color display is minimized bypositioning the film-based lightguide within the display or using thefilm-based lightguide as a substrate for a layer or material of thedisplay (such as, for example, the substrate for the color filter layer,transparent conductor layer, adhesive layer, or electro-optical materiallayer). In one embodiment, the light emitting device includes aplurality of light absorbing adhesive regions that adhere to one or morelayers of the display or film-based lightguide (such as on the claddinglayer of the film-based lightguide or on the electro-optical materiallayer).

In one embodiment, the light emitting device includes a film-basedlightguide and a force sensitive touchscreen wherein the film basedlightguide is sufficiently thin to permit a force sensitive touchscreento function by finger pressure on the display.

In one embodiment, a film-based lightguide frontlight is disposedbetween a touchscreen film and a reflective spatial light modulator. Inanother embodiment, a touchscreen film is disposed between thefilm-based lightguide and the reflective spatial light modulator. Inanother embodiment, the reflective spatial light modulator, thefilm-based lightguide frontlight and the touchscreen are all film-baseddevices and the individual films may be laminated together. In anotherembodiment, the light transmitting electrically conductive coating forthe touchscreen device or the display device is coated onto thefilm-based lightguide frontlight. In a further embodiment, thefilm-based lightguide is physically coupled to the flexible electricalconnectors of the display or the touchscreen. In one embodiment, theflexible connector is a “flexible cable”, “flex cable,” “ribbon cable,”or “flexible harness” including a rubber film, polymer film, polyimidefilm, polyester film or other suitable film.

In one embodiment, a reflective display includes one or more film-basedlightguides disposed within or adjacent to one or more regions selectedfrom the group: the region between the touchscreen layer and thereflective light modulating pixels, the region on the viewing side ofthe touchscreen layer, the region between a diffusing layer and thereflective light modulating pixels, the viewing side of the diffusinglayer in a reflective display, the region between a diffusing layer andthe light modulating pixels, the region between the diffusing layer andthe reflective element, the region between the light modulating pixelsand a reflective element, the viewing side of a substrate for acomponent or the light modulating pixels, the reflective display,between the color filters and the spatial light modulating pixels, theviewing side of the color filters, between the color filters and thereflective element, the substrate for the color filter, the substratefor the light modulating pixels, the substrate for the touchscreen, theregion between a protective lens and the reflective display, the regionbetween a light extraction layer and the light modulating pixels, theregion on the viewing side of a light extraction layer, the regionbetween an adhesive and a component of a reflective display, and betweentwo or more components of a reflective display known in the art. In theaforementioned embodiment, the film-based lightguide may includevolumetric light extraction features or light extraction features on oneor more surfaces of the lightguide and the lightguide may include one ormore lightguide regions, one or more cladding regions, or one or moreadhesive regions.

In one embodiment, the film-based lightguide is folded around a firstedge of the active area of a reflective spatial light modulator behind areflective spatial light modulator and one or more selected from thegroup: a touchscreen connector, touchscreen film substrate, reflectivespatial light modulator connector, and reflective spatial lightmodulator film substrate is folded behind the first edge, a second edgessubstantially orthogonal to the first edge, or an opposite edge to thefirst edge. In the aforementioned embodiment, a portion of thelightguide region, light mixing region, or coupling lightguide includesthe bend region of the fold and may extend beyond the reflective spatiallight modulator flexible connector, reflective spatial light modulatorsubstrate, touchscreen flexible connector or touchscreen flexiblesubstrate.

Backlight or Frontlight

In one embodiment, the film-based lightguide illuminates a display,forming an electroluminescent display. In one embodiment, the film basedlightguide is a frontlight for a reflective or transflective display. Inanother embodiment, the film-based lightguide is a backlight for atransmissive or transflective display. Typically, with displaysincluding light emitting lightguides for illumination, the location ofthe lightguide will determine whether or not it is considered abacklight or frontlight for an electroluminescent display wheretraditionally a frontlight lightguide is a lightguide disposed on theviewing side of the display (or light modulator) and a backlightlightguide is a lightguide disposed on the opposite side of the display(or light modulator) than the viewing side. However, the frontlight orbacklight terminology to be used can vary in the industry depending onthe definition of the display or display components, especially in thecases where the illumination is from within the display or withincomponents of the spatial light modulator (such as the cases where thelightguide is disposed in-between the liquid crystal cell and the colorfilters or in-between the liquid crystal materials and a polarizer in anLCD). In some embodiments, the lightguide is sufficiently thin to bedisposed within a spatial light modulator, such as between lightmodulating pixels and a reflective element in a reflective display. Inthis embodiment, light can be directed toward the light modulatingpixels directly or indirectly by directing light to the reflectiveelement such that is reflects and passes through the lightguide towardthe spatial light modulating pixels. In one embodiment, a lightguideemits light from one side or both sides and with one or two lightdistribution profiles that contribute to the “front” and/or “rear”illumination of light modulating components. In embodiments disclosedherein, where the light emitting region of the lightguide is disposedbetween the spatial light modulator (or electro-optical regions of thepixels, sub-pixels, or pixel elements) and a reflective component of areflective display, the light emitting from the light emitting regionmay propagate directly toward the spatial light modulator or indirectlyvia directing the light toward a reflective element such that the lightreflected passes back through the lightguide and into the spatial lightmodulator. In this specific case, the terms “frontlight” and “backlight”used herein may be used interchangeably.

In one embodiment, a light emitting display backlight or frontlightincludes a light source, a light input coupler, and a lightguide. In oneembodiment, the frontlight or backlight illuminates a display or spatiallight modulator selected from the group: transmissive display,reflective display, liquid crystal displays (LCD's), MEMs based display,electrophoretic displays, cholesteric display, time-multiplexed opticalshutter display, color sequential display, interferometric modulatordisplay, bistable display, electronic paper display, LED display, TFTdisplay, OLED display, carbon nanotube display, nanocrystal display,head mounted display, head-up display, segmented display, passive matrixdisplay, active matrix display, twisted nematic display, in-planeswitching display, advanced fringe field switching display, verticalalignment display, blue phase mode display, zenithal bistable device,reflective LCD, transmissive LCD, electrostatic display, electrowettingdisplay, bistable TN displays, micro-cup EPD displays, grating alignedzenithal display, photonic crystal display, electrofluidic display, andelectro chromic displays.

LCD Backlight or Frontlight

In one embodiment, a backlight or frontlight suitable for use with aliquid crystal display panel includes at least one light source, lightinput coupler, and lightguide. In one embodiment, the backlight orfrontlight includes a single lightguide wherein the illumination of theliquid crystal panel is white. In another embodiment, the backlight orfrontlight includes a plurality of lightguides disposed to receive lightfrom at least two light sources with two different color spectra suchthat they emit light of two different colors. In another embodiment, thebacklight or frontlight includes a single lightguide disposed to receivelight from at least two light sources with two different color spectrasuch that they emit light of two different colors. In anotherembodiment, the backlight or frontlight includes a single lightguidedisposed to receive light from a red, green and blue light source. Inone embodiment, the lightguide includes a plurality of light inputcouplers wherein the light input couplers emit light into the lightguidewith different wavelength spectrums or colors. In another embodiment,light sources emitting light of two different colors or wavelengthspectrums are disposed to couple light into a single light inputcoupler. In this embodiment, more than one light input coupler may beused and the color may be controlled directly by modulating the lightsources.

In a further embodiment, the backlight or frontlight includes alightguide disposed to receive light from a blue or UV light emittingsource and further includes a region including a wavelength conversionmaterial such as a phosphor film. In another embodiment, the backlightincludes 3 layers of film lightguides wherein each lightguideilluminates a display with substantially uniform luminance when thecorresponding light source is turned on. In this embodiment, the colorgamut can be increased by reducing the requirements of the color filtersand the display can operate in a color sequential mode or all-colors-onsimultaneously mode. In a further embodiment, the backlight orfrontlight includes 3 layers of film lightguides with 3 spatiallydistinct light emitting regions including light extraction featureswherein each light extraction region for a particular lightguidecorresponds to a set of color pixels in the display. In this embodiment,by registering the light extracting features (or regions) to thecorresponding red, green, and blue pixels (for example) in a displaypanel, the color filters are not necessarily needed and the display ismore efficient. In this embodiment, color filters may be used, however,to reduce crosstalk.

Reflective Display

In one embodiment, a method of producing a display includes: forming anarray of coupling lightguides from a lightguide region of a filmincluding a core region and a cladding region by separating the couplinglightguides from each other such that they remain continuous with thelightguide region of the film and include bounding edges at the end ofthe coupling lightguides; folding the plurality of coupling lightguidessuch that the bounding edges are stacked; directing light from a lightsource into the stacked bounding edges such that light from the lightsource propagates within the core region through the couplinglightguides and lightguide region of the film by total internalreflection; forming light extraction features on or within the corelayer in a light emitting region of the lightguide region of the film;disposing a light extracting region on the cladding region or opticallycoupling a light extracting region to the cladding region in a lightmixing region of the lightguide region between the coupling lightguidesand the light emitting region; and disposing the light emitting regionadjacent a reflective spatial light modulator.

Multiple Light Emitting Areas or Displays

In one embodiment, the light emitting device includes two or more lightemitting areas or displays defined by regions with one or moreproperties selected from the group: emit different color gamuts; emitlight within different functional areas of the display; emit light withdifferent angular properties; emit light to illuminate a button, key,keyboard area, or other user interface region; have different sizes orshapes; and are positioned on different sides or surfaces of the device.In one embodiment, the light emitting device includes two or more lightemitting regions with different use modes or different illuminationmodes. A different illumination mode can include one or more differentlight output properties selected from the group: different times in the“on” state or “off” state of illumination; different frequencies ofillumination; different durations of illumination; different colors ofillumination; different color gamuts; different angular light outputprofiles; different spatial light output profiles; different spatialluminance uniformity; and different color, luminances or luminousintensity at a specific angle. For example, in one embodiment, the lightemitting device illuminates a main display and a sub-display. The maindisplay and sub-display could be two light emitting areas defined by thesame spatial light modulator or two light emitting areas defined by twoseparate spatial light modulators. In one embodiment, each lightemitting area or display may be illuminated by the same or differentlightguides and/or light sources. For example, in one embodiment, thelight emitting device has a high color gamut lightguide positioned toilluminate the main display of a device with a main display andsub-display from the front in a first mode using light from monochromered, green, and blue LEDs. In this embodiment, the sub-display can beilluminated by a second lightguide that emits only white light to reducethe power required for illuminating the sub-display (which could includeicons or keys, for example) to the same luminance. In anotherembodiment, a first display region includes an array of color filtersand a second display region does not include an array of color filters.For example, in one embodiment, the sub-display may be designed withouta color filter array such that the monochrome sub-display illuminated bya white (or monochrome) light source can operate at a significantlylower power for the same luminance as the main display with colorfilters since light is not absorbed by a color filter array.

In one embodiment, the device includes two or more lightguides spatiallyseparated in the plane of the active area of the light emitting devicesuch that they can be illuminated independently. In this embodiment, forexample, the edges of one or more lightguides opposite the side of thelightguide with the light input coupler may include a light reflectiveor absorptive coating to prevent light from exiting one lightguide andentering into an adjacent lightguide. In one embodiment, the spatiallyseparated lightguides permit the light emitting display device to have asubstantially uniform thickness.

Light Emitting Device Assembly

In one embodiment, the film-based lightguide is adhered to a display,component of a display, or other component of a light emitting deviceusing lamination and/or one or more of the following: addition ofpressure, addition of heat, laminating a coated layer or region,laminating to a relative position maintaining element, and coating anadhesive onto a substrate or component and joining one component toanother.

In one embodiment, the adhesive functions as a cladding between the coreregion of the lightguide and another component, and reduces the flux oflight absorbed by the RPME due to the lightguide contacting the RPME. Inanother embodiment, the pressure sensitive adhesive increases the yieldstrength or impact strength (Izod or Charpy impact strength, forexample) of the film-based lightguide, light emitting device, and/ordisplay. In one embodiment, an adhesive is positioned between thelightguide and a reflective film, surface of the relative positionmaintaining element, or optical component disposed to receive light fromthe light source and direct it into the input surface of the stack ofcoupling lightguides.

Method of Manufacturing Light Input/Output Coupler

In one embodiment, the lightguide and light input or output coupler areformed from a light transmitting film by creating segments of the filmcorresponding to the coupling lightguides and translating and bendingthe segments such that a plurality of segments overlap. In a furtherembodiment, the input surfaces of the coupling lightguides are arrangedto create a collective light input surface by translation of thecoupling lightguides to create at least one bend or fold.

Film Production

In one embodiment, the film or lightguide is one selected from thegroup: extruded film, co-extruded film, cast film, solvent cast film, UVcast film, pressed film, injection molded film, knife coated film, spincoated film, and coated film. In one embodiment, one or two claddinglayers are co-extruded on one or both sides of a lightguide region. Inanother embodiment, tie layers, adhesion promotion layers, materials orsurface modifications are disposed on a surface of or between thecladding layer and the lightguide layer. In one embodiment, the couplinglightguides, or core regions thereof, are continuous with the lightguideregion of the film as formed during the film formation process. Forexample, coupling lightguides formed by slicing regions of a film atspaced intervals can form coupling lightguides that are continuous withthe lightguide region of the film. In another embodiment, a film-basedlightguide with coupling lightguides continuous with the lightguideregion can be formed by injection molding or casting a material in amold including a lightguide region with coupling lightguide regions withseparations between the coupling lightguides. In one embodiment, theregion between the coupling lightguides and lightguide region ishomogeneous and without interfacial transitions such as withoutlimitation, air gaps, minor variations in refractive index,discontinuities in shapes or input-output areas, and minor variations inthe molecular weight or material compositions.

In another embodiment, at least one selected from the group: lightguidelayer, light transmitting film, cladding region, adhesive region,adhesion promotion region, or scratch resistant layer is coated onto oneor more surfaces of the film or lightguide. In another embodiment, thelightguide or cladding region is coated onto, extruded onto or otherwisedisposed onto a carrier film. In one embodiment, the carrier filmpermits at least one selected from the group: easy handling, fewerstatic problems, the ability to use traditional paper or packagingfolding equipment, surface protection (scratches, dust, creases, etc.),assisting in obtaining flat edges of the lightguide during the cuttingoperation, UV absorption, transportation protection, and the use ofwinding and film equipment with a wider range of tension and flatness oralignment adjustments. In one embodiment, the carrier film is removedbefore coating the film, before bending the coupling lightguide, afterfolding the coupling lightguides, before adding light extractionfeatures, after adding light extraction features, before printing, afterprinting, before or after converting processes (further lamination,bonding, die cutting, hole punching, packaging, etc.), just beforeinstallation, after installation (when the carrier film is the outersurface), and during the removal process of the lightguide frominstallation. In one embodiment, one or more additional layers arelaminated in segments or regions to the core region (or layers coupledto the core region) such that there are regions of the film without theone or more additional layers. For example, in one embodiment, anoptical adhesive functioning as a cladding layer is optically coupled toa touchscreen substrate; and an optical adhesive is used to opticallycouple the touchscreen substrate to the light emitting region offilm-based lightguide, thus leaving the coupling lightguides without acladding layer for increased input coupling efficiency.

In another embodiment, the carrier film is slit or removed across aregion of the coupling lightguides. In this embodiment, the couplinglightguides can be bent or folded to a smaller radius of curvature afterthe carrier film is removed from the linear fold region.

Relative Position Maintaining Element

In one embodiment, at least one relative position maintaining elementsubstantially maintains the relative position of the couplinglightguides in the region of the first linear fold region, the secondlinear fold region or both the first and second linear fold regions. Inone embodiment, the relative position maintaining element is disposedadjacent the first linear fold region of the array of couplinglightguides such that the combination of the relative positionmaintaining element with the coupling lightguide provides sufficientstability or rigidity to substantially maintain the relative position ofthe coupling lightguides within the first linear fold region duringtranslational movements of the first linear fold region relative to thesecond linear fold region to create the overlapping collection ofcoupling lightguides and the bends in the coupling lightguides. Therelative position maintaining element may be adhered, clamped, disposedin contact, disposed against a linear fold region or disposed between alinear fold region and a lightguide region. The relative positionmaintaining element may be a polymer or metal component that is adheredor held against the surface of the coupling lightguides, light mixingregion, lightguide region or film at least during one of thetranslational steps. In one embodiment, the relative positionmaintaining element is a polymeric strip with planar or saw-tooth-liketeeth adhered to either side of the film near the first linear foldregion, second linear fold region, or both first and second linear foldregions of the coupling lightguides. By using saw-tooth-like teeth, theteeth can promote or facilitate the bends by providing angled guides. Inanother embodiment, the relative position maintaining element is amechanical device with a first clamp and a second clamp that holds thecoupling lightguides in relative position in a direction parallel to theclamps parallel to the first linear fold region and translates theposition of the clamps relative to each other such that the first linearfold region and the second linear fold region are translated withrespect to each other to create overlapping coupling lightguides andbends in the coupling lightguides. In another embodiment, the relativeposition maintaining element maintains the relative position of thecoupling lightguides in the first linear fold region, second linear foldregion, or both the first and second linear fold regions and provides amechanism to exert force upon the end of the coupling lightguides totranslate them in at least one direction.

In another embodiment, the relative position maintaining elementincludes angular teeth or regions that redistribute the force at thetime of bending at least one coupling lightguide or maintains an evenredistribution of force after at least one coupling lightguide is bentor folded. In another embodiment, the relative position maintainingelement redistributes the force from bending and pulling one or morecoupling lightguides from a corner point to substantially the length ofan angled guide. In another embodiment, the edge of the angled guide isrounded.

In another embodiment, the relative position maintaining elementredistributes the force from bending during the bending operation andprovides the resistance to maintain the force required to maintain a lowprofile (short dimension in the thickness direction) of the couplinglightguides. In one embodiment, the relative position maintainingelement includes a low contact area region, material, or surface reliefregions operating as a low contact area cover, or region wherein one ormore surface relief features are in physical contact with the region ofthe lightguide during the folding operation and/or in use of the lightemitting device. In one embodiment, the low contact area surface relieffeatures on the relative position maintaining element reduce decouplingof light from the coupling lightguides, lightguide, light mixing region,lightguide region, or light emitting region.

In a further embodiment, the relative position maintaining element isalso a thermal transfer element. In one embodiment, the relativeposition maintaining element is an aluminum component with angled guidesor teeth that is thermally coupled to an LED light source.

In another embodiment, a method of manufacturing a lightguide and lightinput coupler including a light transmitting film with a lightguideregion continuously coupled to each coupling lightguide in an array ofcoupling lightguides where the array of coupling lightguides include afirst linear fold region and a second linear fold region substantiallyparallel to the first fold region, includes the steps: (a) forming anarray of coupling lightguides physically coupled to a lightguide regionin a light transmitting film by physically separating at least tworegions of a light transmitting film in a first direction; (b)increasing the distance between the first linear fold region and thesecond linear fold region of the array of coupling lightguides in adirection perpendicular to the light transmitting film surface at thefirst linear fold region; (c) decreasing the distance between the firstlinear fold region and the second linear fold region of the array ofcoupling lightguides in a direction substantially perpendicular to thefirst linear fold region and parallel to the light transmitting filmsurface at the first linear fold region; (d) increasing the distancebetween the first linear fold region and the second linear fold regionof the array of coupling lightguides in a direction substantiallyparallel to the first linear fold region and parallel to the lighttransmitting film surface at the first linear fold region; and (e)decreasing the distance between the first linear fold region and thesecond linear fold region of the array of coupling lightguides in adirection perpendicular to the light transmitting film surface at thefirst linear fold region; such that the coupling lightguides are bent,disposed substantially one above another, and aligned substantiallyparallel to each other.

In one embodiment, the RPME includes alignment guides such as holes,ridges, openings, teeth, protrusions, or connectors, on one, two, three,or four sides of the RPME. For example, in one embodiment, the RPME islonger in a first direction than a second orthogonal direction andincludes one or more alignment holes near the two ends in the longerdirection. In one embodiment, one or more alignment guides is positionedon the side of the RPME opposite the teeth in the second orthogonaldirection.

Perforated Areas

In one embodiment, the light emitting device includes one or morefunctional layers selected from the group: the film-based lightguide;cladding layer of the film based lightguide; touchscreen layer orsubstrate; hardcoating layer or substrate; anti-glare layer orsubstrate; color filter layer or substrate; electro-optic layer orsubstrate; reflective material, film, layer, or substrate; polarizerlayer or substrate; light redirecting layer or substrate; lightextraction feature film, layer or substrate; impact protection layer orsubstrate; internal coating or layer; conformal coating or layer;circuit board or layer; thermally conducting film, layer or substrate;sealant layer or substrate; spacer layer or substrate; electricallyconducting layer (transparent or opaque) or substrate; anode layer orsubstrate; cathode layer or substrate; active matrix layer or substrate;and passive matrix layer or substrate. In one embodiment, at least onefunctional layer is perforated to allow for tearing of the functionallayer or substrate before, during, or after assembly, forming thecoupling lightguides, folding the coupling lightguides, stacking theends of the coupling lightguides, or adhering the lightguide to adisplay.

Folding and Assembly

In one embodiment, the coupling lightguides are heated to soften thelightguides during the folding or bending step. In another embodiment,the coupling lightguides are folded while they are at a temperatureabove one selected from the group: 50 degrees Celsius, 70 degreesCelsius, 100 degrees Celsius, 150 degrees Celsius, 200 degrees Celsius,and 250 degrees Celsius.

Folder

In one embodiment, the coupling lightguides are folded or bent usingopposing folding mechanisms. In another embodiment, grooves, guides,pins, or other counterparts facilitate the bringing together opposingfolding mechanisms such that the folds or bends in the couplinglightguides are correctly folded. In another embodiment, registrationguides, grooves, pins or other counterparts are disposed on the folderto hold in place or guide one or more coupling lightguides or thelightguide during the folding step.

Assembly Order

In one embodiment, the film-based lightguide includes an array ofcoupling lightguides and the array of coupling lightguides are foldedprior to physically or optically coupling the film-based lightguide tothe light emitting device, display or a component thereof. In anotherembodiment, the array of coupling lightguides are folded afterphysically or optically coupling the film-based lightguide to the lightemitting device, display or a component thereof. In another embodiment,the light emitting device or display includes a light input couplerincluding a folded, stacked array of coupling lightguides and the lightinput coupler is assembled before or after the film-based lightguide islaminated to the display. In one embodiment, the display functions as arelative position maintaining element and adhering the film-basedlightguide to the display maintains the relative position of thecoupling lightguides during the subsequent folding operation.

Guide for Bend or Fold

In one embodiment, a lightguide or light emitting device comprises aguide for one or more bends or folds. In this embodiment, the guide isan element with at least one curved surface adjacent a curved innersurface of the film at the bend. In one embodiment, the guide limits theradius of curvature of the bend or fold such that the film does notcrease, tear, craze, or crack in the fold or bend region. In oneembodiment, the curved surface of the guide is in contact with the innersurface of the film and when tension is applied to the film (such aswhen a film is pulled behind itself), the guide surface ensures aminimum radius of curvature for the film. In one embodiment, the guidecan help protect against crushing, creasing, or wrinkling of the filmduring handling, device assembly, or during the folding or bending step.In one embodiment, a lightguide comprises a film with a light emittingregion and an array of coupling lightguides extending from a body of thefilm and the film is folded behind itself at a first fold; and a guidecomprising a first curved surface adjacent an inner surface of the filmat the first fold. In one embodiment, a lightguide comprises a film witha light mixing region disposed along the film between the light emittingregion and an array of coupling lightguides extending from the film, thelight mixing region is folded at a first fold such that a portion of thelight mixing region is behind the light emitting region; and a firstguide with a first curved surface adjacent an inner surface of the lightmixing region of the film. In another embodiment, the light emittingregion of the film folds behind itself at a first fold and the guide ispositioned adjacent the light emitting region at the fold.

The guide may be formed from a metal, polymer, plastic, rubber, foamrubber, glass, inorganic material, organic material, or a combinationthereof. In one embodiment, the guide is a component located within thefold or bend of the film and may be free-standing, physically coupled,operatively coupled, or mechanically coupled to a component of thedevice. The guide may be solid or hollow. In one embodiment the guide isa surface of a device element such as the film, display, displaysubstrate, glass substrate, glass substrate of a display, display frame,backlight frame, frontlight frame, light fixture frame, display lens orcover, display module, housing, housing for the light input coupler,frame, circuit board, electrical or mechanical connector, a hinge, agasket, connector, relative position maintaining element, component ofthe light emitting device, thermal transfer element (such as a heatsink), or rolled-up portion of the film (such as a light mixing regionwrapped around the coupling lightguides to form a shape with a curvedsurface that is used for the guide). In another embodiment, the guide isa separate component comprising a curved surface adjacent the innersurface of the film at the fold or bend wherein the guide is operativelycoupled, physically coupled, adhered, or glued to one or more componentsselected from the group: film, display, display substrate, glasssubstrate, glass substrate of a display, display frame, backlight frame,frontlight frame, light fixture frame, display lens or cover, displaymodule, housing, housing for the light input coupler, frame, circuitboard, electrical or mechanical connector, a hinge, a gasket, connector,relative position maintaining element, thermal transfer element,component of the light emitting device, and an intermediate componentoperatively coupled to one or more of the aforementioned components.

Guide Surface

In one embodiment, the surface of the guide adjacent the inner surfaceof the film at the fold or bend is curved in a first plane comprisingthe fold or bend of the film. In one embodiment, the curved surface ofthe guide or a portion of the curved surface of the guide adjacent theinner surface of the film at the fold or bend in a plane comprising thefold or bend of the film comprises a subtended angle from a point at themidpoint of the line between a point on the inner surface of the film atthe start of the fold or bend and the point on the inner surface of thefilm at the end of the fold or bend, and the subtended angle is one ormore selected from the group: greater than 45 degrees, greater than 80degrees, 90 degrees, greater than 90 degrees, greater than 135 degrees,180 degrees, greater than 180 degrees, greater than 270 degrees, between45 degrees and 360 degrees, between 80 degrees and 360 degrees, between80 degrees and 270 degrees.

In one embodiment, the cross-sectional shape of the surface of the guideadjacent the inner surface of the film in the fold or bend regioncomprises all, a portion, or a combination of a circle, semicircle,oval, ellipse, parabola, or hyperbola.

In one embodiment, the curved surface of the guide or a portion of thecurved surface of the guide adjacent the inner surface of the film atthe fold or bend in a plane comprising the fold or bend of the film hasa radius of curvatures or average radius of curvature less than oneselected from the group: 1, 2, 4, 8, 10, 20, 30, 50, 100, 200 and 400millimeters. In embodiments where the radius of curvature of the surfaceof the guide is not uniform, the average radius of curvature is theaverage radius of curvature of the surface in the region of the surfaceof the guide adjacent the inner surface of the film. In anotherembodiment the curved surface of the guide or the portion of the curvedsurface of the guide adjacent the inner surface of the film at the foldor bend has a radius of curvatures or average radius of curvaturegreater than one selected from the group: 1, 2, 4, 8, 10, 20, 30, 50,100, 200 and 400 millimeters. In this embodiment, the guide can maintainthe minimum radius of curvature for the film at the fold to 4millimeters, for example.

In one embodiment, the curved surface of the guide or a portion of thecurved surface of the guide adjacent the inner surface of the film atthe fold or bend in a plane comprising the fold or bend of the film hasa radius of curvatures or average radius of curvature less than oneselected from the group: 2, 4, 8, 10, 20, 30, and 50 times the averagethickness of the film at the fold or bend. In another embodiment thecurved surface of the guide or the portion of the curved surface of theguide adjacent the inner surface of the film at the fold or bend has aradius of curvatures or average radius of curvature greater than oneselected from the group: 0.5, 1, 2, 3, 4, 8, 10, 20, and 30 times theaverage thickness of the film at the fold or bend. In this embodiment,the guide can maintain the minimum radius of curvature for the film atthe fold to greater than 2 times the average thickness of the film atthe fold or bend, for example.

In one embodiment, a reflective display comprises reflective spatiallight modulator (SLM), a frontlight comprising a film with a lightemitting region positioned adjacent a top surface of the reflective SLMon the viewing side of the reflective SLM and configured to extractlight toward the reflective SLM, wherein the film is folded behind andadjacent a bottom surface of the reflective SLM at a first fold and theratio of the radius of curvature or average radius of curvature of asurface of the guide adjacent the inner surface of the film at the foldin a plane comprising the fold to the thickness of the reflective SLMfrom the top surface to the bottom surface in a plane comprising thefold is greater than one selected from the group: 0.5, 0.75, 1, 1.25,1.5, 1.75, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, and 10.

In one embodiment, the inner surface of the film is in contact with theouter surface of the guide at the fold or bend and, in a planecomprising the fold or bend, the radius of curvature or average radiusof curvature of the film at the fold or bend along the inner filmsurface in contact with the outer surface of the guide is substantiallythe same as the radius of curvature or average radius of curvature ofthe outer guide surface in contact with the inner surface of the film atthe fold or bend.

In one embodiment, the surface of the guide adjacent the film at thefold or bend is smooth, rough, comprises surface undulations, surfacegrooves, surface pits, or raised surface relief structures. In oneembodiment, the non-smooth surface reduces the surface area of the guidein contact with the film and can reduce the friction when the film ispulled or folded behind itself while maintaining a minimum radius ofcurvature for the fold or bend.

In one embodiment, the cross-section of the guide at the surface of theguide adjacent the inner surface of the film at the fold or bend in aplane comprising the fold or bend is substantially constant in adirection perpendicular to the plane comprising the fold or bend. Forexample, in one embodiment, the guide has a shape of substantially halfof a rod with a semicircular cross-section, with a length more thanthree times it's width in a plane comprising the fold of the film, and asurface adjacent the inner surface of the film with a cross-sectioncomprising an arc subtending a 180 degrees in the plane comprising thefold.

Frame

In one embodiment, one or more relative position maintaining elementsare operatively coupled to a frame. In one embodiment, the frameincludes a perimeter region and an interior opening. The interioropening can reduce the weight and material costs of the frame, relativeto a sheet, for example. In one embodiment, the frame is thermallycoupled to a light source such that the frame transfers heat away fromthe light source through conduction. For example, in one embodiment, thelight source is an LED and is thermally coupled to a metal core circuitboard that is thermally coupled to the frame. In another embodiment, alight emitting device includes a film-based lightguide that isoperatively coupled to the frame. For example, in one embodiment, thefilm-based lightguide is adhered along one or more sides of a frame. Inanother embodiment, the length and width of the frame are greater than 5times the average thickness of the frame. In another embodiment, theframe has a top surface opposite the bottom surface in the thicknessdirection and the film-based lightguide is operatively coupled to theframe on the top surface, the bottom surface, or both the top and bottomsurfaces. In another embodiment, the film-based lightguide isoperatively coupled to the top surface and the bottom surface of theframe along the same surface of the lightguide. In one embodiment, thefilm is operatively coupled to the frame through an intermediatematerial or component, such as film, optical film, reflective film,frame clamp, fastener, adhesive, housing or housing component, or otherelement of the light emitting device. In another embodiment, thelightguide is operatively coupled to the frame such that the frameprevents the lightguide from unfolding due to residual stress remainingin the lightguide. In another embodiment, the frame includes one or morecurved surfaces or edges along one or more sides to increase the contactsurface of the frame with the film-based lightguide and reduce thelikelihood of a tear. In one embodiment, a frame includes a curvedregion with a radius of curvature less than one selected from the group:1, 2, 4, 8, 10, 20, 30, 50, 100, 200 and 400 millimeters. In oneembodiment, the width and/or the length dimension of the frame isgreater than the corresponding length or width dimension of the lightemitting area of the film-based lightguide. In another embodiment, thewidth and/or the length of the frame is equal to the correspondinglength or width dimension of the light emitting area of the film-basedlightguide. In one embodiment, the width and/or the length dimension ofthe frame is less than the corresponding length or width dimension ofthe light emitting area of the film-based lightguide. In anotherembodiment, the width and/or the length dimension of the frame is lessthan the corresponding length or width dimension of the light emittingarea of the film-based lightguide corresponding to the area illuminatinga display. In another embodiment, the length or width dimension of therelative position maintaining element is less than the distance betweentwo attachment mechanisms operatively configured to couple to therelative position maintaining element along opposite sides of the frame.

Attachment Mechanisms for Securing Components to the Frame

In one embodiment, the frame includes a plurality of attachmentmechanisms on one or more sides or internal regions that facilitate thecoupling of the frame to one or more components selected from the group:one or more relative position maintaining elements, one or more lightsources, one or more printed circuit boards, a housing, one or morefilms, one or more optical films, one or more reflective films, one ormore film-based lightguides, one or more reflective displays, one ormore transmissive displays, one or more transflective displays, aflexible electrical connector, one or more heat sinks, one or morethermal conducting elements, one or more optical elements, one or morebatteries, one or more touch sensors (including switches or capacitivetouch sensors), a touch screen, and a ground connector. In oneembodiment, the attachment mechanism includes one or more fastenersselected from the group: holes, cavities, recessed regions, protrusions,pins, threaded fasteners, screws, bolts, nuts, screw holes, fixed orbendable tabs operatively configured to attach components, adhesive,clamps, clasps, flanges, latches, retainers, rivets, and stitches.

In one embodiment, the frame includes a plurality of attachmentmechanisms that facilitate the coupling of the relative positionmaintaining element to the frame. For example, in one embodiment, theattachment mechanisms are tabs including one or more holes orprotrusions. In this example, protrusions in the relative positionmaintaining element may operatively couple with holes in the tabs orholes in the relative position maintaining element may operativelycouple with pins in the tabs on opposite sides of a frame. In oneembodiment, attachment mechanisms on the frame are inset from the outeredges of the frame such that the corresponding attachment mechanisms onthe component to which it is attached do not extend past the outer edgesof the frame along one or more sides. For example, in one embodiment, analuminum frame includes two attachment tabs on opposite sides in thewidth direction. In this embodiment, the frame tabs are set inwards fromouter edge of the frame, by 3 millimeters for example, such that thepins protruding from opposite ends of a relative position maintainingelement, protruding by 3 millimeters for example, do not extend past theedge of the frame when they are engaged into holes in the frame tabs. Inanother embodiment, a frame for a light emitting device includes one ormore tabs configurable to operatively couple a relative positionmaintaining element to the frame wherein the tabs have an inset distancefrom the closest length or width edge of the frame greater than oneselected from the group: 1, 2, 4, 8, 10, 20, 30, 50, 100, 200 and 400millimeters.

In this embodiment, the width of the frame can be less than or equal tothe width of the light emitting area of the light emitting device ordisplay to enable a minimal frame (or border or bezel) around the lightemitting area of the light emitting device or display. In anotherembodiment, the relative position maintaining element or housingincluding the relative position maintaining element or light sourceincludes a recessed cavity or notch into which tabs on a frame can beinserted. For example, in one embodiment, tabs on an aluminum frame areinserted into an opening in a relative position maintaining element (orhousing or other element operatively coupled to the relative positionmaintaining element) such that a mechanical force, such as from a springor a restoring force from the elastic modulus in the tabs when insertedinto the opening, forces contact between the tabs and a thermalconducting element. In this embodiment, the thermal conducting elementis thermally coupled to a light emitting diode such that a conductiveheat path is created between the light source and the frame. In anotherembodiment, the thermal conducting element includes one or more selectedfrom the group: heat sink, metal core circuit board, thermallyconductive adhesive or epoxy, thermally conductive pad, thermallyconductive grease or gel, solder, component including copper, componentincluding aluminum, component including a ceramic material, metalcomponent, heat sink, and heat pipe. In one embodiment, the frame is aheat sink for the light source and is thermally coupled to the lightsource using a thermally conductive element. For example, in oneembodiment, one or more LEDs are thermally coupled to an aluminum frame(such by thermally coupling to the frame through the frame's attachmentmechanisms or directly thermally coupled to the frame) using a thermallyconductive adhesive.

In another embodiment, the frame includes one or more attachmentmechanisms in an interior region of the frame that is continuous withmore than one side of the frame. For example, in one embodiment, theframe includes an opening that only extends across half of the length ofthe frame and the frame includes attachment one or more attachmentmechanisms in the interior region outside the opening.

In one embodiment, the frame includes one or more tabs that are bent orinclude a curve or turn that operatively couples one or more opticalfilms to the frame. For example, in one embodiment, an aluminum frameincludes bent tabs (or regions with an angled or curved surface)creating openings along two sides and bendable tabs along opposite sidesthat enable optical films to be positioned on the frame, into theopenings, and operatively coupled to the frame after bending thebendable tabs. In another embodiment, the frame includes one or moreregistration pins positioned outside the region corresponding to thelight emitting area of the film-based lightguide when it is operativelycoupled to the frame. For example, in one embodiment, a frame includesregistration pins extending from the top surface of the frame along itsperiphery and one or more optical films include holes (or grooves thatallow for film thermal expansion) that align with the pins when thefilms are operatively coupled to the frame.

In another embodiment, the frame includes two or more components, suchas a top section and a bottom section that can be operatively coupled toeach other. For example, in one embodiment, a frame includes a bottomsection operatively coupled to a relative position maintaining elementand a top section. In this embodiment, one or more optical films and/orlightguides can be operatively coupled to the top section of the frameand when the top section is operatively coupled to the bottom sectionthe frame, the frame operatively couples one or more optical filmsand/or lightguides to the relative position maintaining element.

In one embodiment, the one or more pairs of tabs on opposite sides of aframe (along the width direction, for example) operatively couple arelative position maintaining element to a frame and are positioned onthe frame such that a line between the tabs is not parallel with theedge of the frame joining the two sides (the length edge, for example).In this embodiment, the relative position maintaining element is notparallel to one or more sides of the frame.

In one embodiment, the frame includes at least one support arm extendingfrom a frame side into the interior region or opening of the frame oroutward from the interior region of the frame. In one embodiment, thesupport arm extends into the interior region of the frame and includesone or more tabs operatively coupled to one or more relative positionmaintaining elements. In one embodiment, the length of the support armis less than the length of the opening in one direction. In anotherembodiment, the support arm extends across the length of the opening inone direction and is operatively coupled to two sides of the frame.

The following are more detailed descriptions of various embodimentsillustrated in the Figures.

FIG. 1 is a top view of one embodiment of a light emitting device 100including a light input coupler 101 disposed on one side of a film-basedlightguide. The light input coupler 101 includes coupling lightguides104 and a light source 102 disposed to direct light into the couplinglightguides 104 through a light input surface 103 including input edgesof the coupling lightguides 104. In one embodiment, each couplinglightguide 104 includes a coupling lightguide terminating at a boundingedge. Each coupling lightguide is folded such that the bounding edges ofthe coupling lightguides are stacked to form the light input surface103. The light emitting device 100 further includes a lightguide region106 defining a light mixing region 105, a lightguide 107, and a lightemitting region 108. Light from the light source 102 exits the lightinput coupler 101 and enters the lightguide region 106 of the film. Thislight spatially mixes with light from different coupling lightguides 104within the light mixing region 105 as the light propagates through thelightguide 107. In one embodiment, light is emitted from the lightguide107 in the light emitting region 108 due to light extraction features(not shown). In this embodiment, the light mixing region 105 includes atapered lateral edge 111 that tapers outward from the couplinglightguides 104 to the light emitting region 108. In this embodiment,the tapered edge 111 has an extended direction length 110 and adisplacement 109 from the lateral edge 112 of the lightguide 107 in thelight emitting region 108. When the light input coupler 101 and at leasta portion of the light mixing region 105 of the lightguide 107 arefolded behind the light emitting region 108 of the lightguide 107, thelight source 102 does not extend past the lateral edge 112 of thelightguide 107 in the light emitting region 108.

FIGS. 2 and 3 are side views of one embodiment of a light emittingdevice 200 including a film-based lightguide 220 operatively coupled toa frame 201. In FIGS. 2 and 3 dotted lines are used to referencecomponents behind other components. A plurality of coupling lightguides104 extend from the lightguide 220 and are folded and stacked such thattheir ends 206 are positioned to receive light from the light source102. A relative position maintaining element 207 substantially maintainsthe relative position of the coupling lightguides 104. The relativeposition maintaining element 207 is physically coupled to two tabs 202of the frame 201. The lightguide 220 includes a taper (not shown) in thelight mixing region 219 between the coupling lightguides 104 and thelight emitting region 108 that permits the light source 102 and therelative position maintaining element 207 to remain between the tabs 202of the frame 201 and not extend past the lateral edges 222 of thelightguide 220 in the light emitting region 108 in the y direction. Inthis embodiment, the frame 201 does not extend past the light emittingregion 108 of the lightguide 220 in the y direction (shown in FIG. 3).The lightguide 220 includes a first bend 203 in the light mixing region219 to position the light source 102 and the coupling lightguides 104behind the light emitting region 108 and a second bend 204 in the lightmixing region 219 to position the light source 102 and at least onecoupling lightguide 104 at a distance 209 from the light emitting region108 of the lightguide 220 in the z direction less than the diameter 208of the first bend 203. In this embodiment, the lightguide 220 isoperatively coupled to the frame 201 on the top surface 210 and bottomsurface 211 of the frame 201 and the maximum separation distance 214between inner surface regions 212, 213 of the folded lightguide 220 isgreater than the average separation distance 223 between the lowersurface 215 of the light emitting region 108 of the lightguide 220 andthe upper surface 216 of the portion 218 of the light mixing region 219positioned below the light emitting region 108 (in the −z direction).The shape of the lightguide 220 further includes an inflection point 205in the plane (x-z plane) including the first bend 203.

FIG. 3 is a side view of the light emitting device 200 of FIG. 2illustrating the relative position maintaining element 207 between thetwo tabs 202 of the frame 201. In this embodiment, the light source 102is thermally coupled to the frame 201 to transfer heat through the frame201 and away from the light source 102 (such as an LED, for example).

FIG. 4 is a bottom perspective view of one embodiment of a frame 401 anda relative position maintaining element 402 suitable for use in anembodiment of a light emitting device. The relative position maintainingelement 402 is operatively coupled to the frame 401 using two tabs 403of the frame 401 on opposite sides of the frame 401. The frame 401further includes an opening 404 to reduce the weight of the frame 401while maintaining structural integrity.

FIG. 5 is a top perspective view of the frame 401 of FIG. 4.

FIG. 6 is a perspective view of one embodiment of a frame 601 suitablefor use in a light emitting device. The frame 601 includes first tabs602 on opposite sides of the frame 601 and second tabs 603 on oppositesides of the frame 603. The frame 601 further includes an opening 604 toreduce the weight of the frame 601 while maintaining structuralintegrity.

FIG. 7 is a perspective view of the frame 601 of FIG. 6, a firstrelative position maintaining element 701, and a second relativeposition maintaining element 702. The first relative positionmaintaining element 701 is operatively coupled to the first tabs 602.The first relative position maintaining element 702 is operativelycoupled to the second tabs 603. In this embodiment, for example, theframe 601 can be utilized in a light emitting device with two lightinput couplers for coupling light into two sides of a single lightguideor into two or more lightguides.

FIG. 8 is a side view of one embodiment of a light emitting device 800including a film-based lightguide 803 operatively coupled to a frame201. In this embodiment, the housing 802 includes a relative positionmaintaining element (not shown), a plurality of coupling lightguides(not shown), and a light source (not shown). The housing 802 isphysically coupled to two tabs 202 of the frame 201. The film-basedlightguide 803 includes a first bend 203 in the light mixing region 904(shown in FIG. 9) of the lightguide 803 between the light emittingregion 108 and the housing 802 that positions the housing 802 and itscomponents behind the light emitting region 108 and a second bend 204 inthe light mixing region 219 that positions the housing 802 and itscomponents closer to the light emitting region 108 of the lightguide 803in the z direction. In this embodiment, the lightguide 803 furtherincludes a third bend 801 in the light mixing region 904 of thelightguide 803 to accommodate the long length of the lightguide 803 (inthe x-z plane including the first bend 203, the second bend 204, and thethird bend 801). In this example, the ratio of the length of the lightmixing region 904 to the length of the light emitting region 108 in thex-z plane is greater than 1.

FIG. 9 is side view of the lightguide 803 including the light emittingregion 108, the light mixing region 904 and the relative positionmaintaining element 802 of FIG. 8. The light mixing region 904 isrepresented by a dashed line corresponding to the length of thelightguide 803 between the light emitting region 108 and the relativeposition maintaining element 802 in the x-z plane. In this embodiment,the first bend angle 901 is 180 degrees, the second bend angle 902 is 45degrees, and the third bend angle 903 is 180 degrees.

FIG. 10 is a side view of one embodiment of a light emitting device 1000including a film-based lightguide 1004 operatively coupled to a frame201. In this embodiment, the housing 802 includes a relative positionmaintaining element (not shown), a plurality of coupling lightguides(not shown), and a light source (not shown). The housing 802 isoperatively coupled to two tabs 202 of the frame 201. The film-basedlightguide 1004 includes a first bend 1001 with a first bend angle of180 degrees in the light mixing region of the lightguide 1004 betweenthe light emitting region 108 and the housing 802. In this embodiment,the first bend 1001 positions the housing 802 behind the light emittingregion 108 and closer to the light emitting region 108 of the lightguide1004 in the z direction. In this embodiment, the lightguide 803 furtherincludes a second bend 1002 and a third bend 1003 in the light mixingregion of the lightguide 1004 to accommodate the long length of thelightguide 1004 (in the x-z plane including the first bend 1001, thesecond bend 1002, and the third bend 1003). In this example, the ratioof the length of the light mixing region to the length of the lightemitting region 108 in the x-z plane is greater than 2 and thelightguide 1004 is folded behind itself twice due to the first bend 1001and the second bend 1002. The housing 802 is positioned closer to thelight emitting region 108 of the lightguide 1004 than the sum of thefirst diameter 1011 of the first bend 1001 and the second diameter 1012of the second bend 1002.

FIG. 11 is a side view of one embodiment of a light emitting device 1100including a film-based lightguide 1105 operatively coupled to a frame201. In this embodiment, the housing 802 includes a relative positionmaintaining element (not shown), a plurality of coupling lightguides(not shown), and a light source (not shown). The housing 802 isphysically coupled to two tabs 202 of the frame 201. The film-basedlightguide 1105 includes a first bend 1101 with a first bend angle 1102of 225 degrees in the light mixing region of the lightguide 1105 betweenthe light emitting region 108 and the housing 802 that folds a secondregion 1106 of the lightguide 1105 behind or beneath and closer to thelight emitting region 108 of the lightguide 1105 in the z direction. Inthis embodiment, the lightguide 1105 further includes a second bend 1103with a second bend angle 1104 of 225 degrees in the light mixing regionof the lightguide 1105 to fold the lightguide 1105 behind or beneath andcloser to the second region 1106 of the lightguide 1105 and the lightemitting region 108 of the lightguide 1105 in the z direction. In thisembodiment, the first bend 1101 and the second bend 1103 are in the sameplane (the x-z plane) and in the light mixing region of the lightguide1105 between the light emitting region 108 and the housing 802. In thisembodiment, the lightguide 1105 includes a third bend 1107 and a fourthbend 1108 that bend the lightguide 1105 to bring it substantiallyparallel with another region of the lightguide 1105 (such as the lightemitting region 108) or component of the light emitting device 1100,such as the frame 201. In the embodiment shown, the third bend 1107bends the lightguide 1105 such that the second region 1106 of thelightguide 1105 is parallel to the light emitting region 108 of thelightguide 1105. The fourth bend 1108 bends the lightguide 1105 suchthat the third region 1110 of the lightguide 1105 between the housing802 and the second bend 1103 is parallel to the light emitting region108 of the lightguide 1105.

FIG. 12 is a bottom view of one embodiment of a frame 1201, a firstrelative position maintaining element 1206, and a second relativeposition maintaining element 1208 suitable for use in an embodiment of alight emitting device. The first relative position maintaining element1206 is operatively coupled to the frame 1201 using a first tab 1204 anda second tab 1205 of the frame 1201 wherein the first tab 1204 extendsfrom a support arm 1207 of the frame 1201 extending into the opening1211 of the frame 1201. The second relative position maintaining element1208 is operatively coupled to the frame 1201 using a third tab 1203 anda fourth tab 1202 of the frame 1201 wherein the third tab 1203 extendsfrom the support arm 1207 of the frame 1201 extending into the opening1211 of the frame 1201. In this embodiment, the support arm 1207 permitstwo relative position maintaining elements 1206, 1208 to be used along afirst side 1212 of the frame 1201 such that a film-based lightguide (notshown) wrapped around the frame 1201 can utilize two light inputcouplers (not shown) along the first side 1212 of the frame 1201.

FIG. 13 is a bottom view of one embodiment of a frame 1301, a firstrelative position maintaining element 1206, a second relative positionmaintaining element 1208, a third relative position maintaining element1306, and a fourth relative position maintaining element 1308 suitablefor use in an embodiment of a light emitting device. In this embodiment,a support arm 1307 extends across the length (x direction) of the frame1301 to create a first opening 1311 and a second opening 1312 within theinterior of the frame 1301. The first relative position maintainingelement 1206 is operatively coupled to the frame 1301 using a first tab1204 and a second tab 1205 of the frame 1301 wherein the first tab 1204extends from the support arm 1307 of the frame 1301. The second relativeposition maintaining element 1208 is operatively coupled to the frame1301 using a third tab 1203 and fourth tab 1202 of the frame 1301wherein the third tab 1203 extends from the support arm 1307 of theframe 1301. The third relative position maintaining element 1306 isoperatively coupled to the frame 1301 using a fifth tab 1304 and a sixthtab 1305 of the frame 1301 wherein the fifth tab 1304 extends from thesupport arm 1307 of the frame 1301. The fourth relative positionmaintaining element 1308 is operatively coupled to the frame 1301 usinga seventh tab 1303 and an eighth tab 1302 of the frame 1301 wherein theseventh tab 1303 extends from the support arm 1307 of the frame 1301. Inthis embodiment, the support arm 1307 permits two relative positionmaintaining elements 1206, 1208 to be used along a first side 1212 ofthe frame 1301 and two relative position maintaining elements 1306, 1308to be used along a second side 1314 of the frame 1301 such that afilm-based lightguide (not shown) wrapped around the frame 1301 on thefirst side 1212 and second side 1314 can utilize two light inputcouplers (not shown) along the first side 1212 of the frame 1301 and twolight input couplers (not shown) along the second side 1314 of the frame1301.

FIG. 14 is a side view of one embodiment of a reflective display 1400including a film lightguide 1407 operatively coupled to a reflectivespatial light modulator 1408. A plurality of coupling lightguides 104extend from the film lightguide 1407 and are folded and stacked suchthat their ends 206 are positioned to receive light from the lightsource 102. A relative position maintaining element 207 substantiallymaintains the relative position of the coupling lightguides 104. Thefilm lightguide 1407 includes a first bend 1406 in the light mixingregion 219 such that a portion 218 of the light mixing region 219 ispositioned behind the light emitting region 108 of the film lightguide1407 and reflective spatial light modulator 1408. A guide 1402 ispositioned within the first bend 1406 such that a first curved surface1401 of the guide 1402 is adjacent the inner surface 1410 of the filmlightguide 1407. In this embodiment, the curved surface 1401 of theguide 1402 adjacent the inner surface 1410 of the film lightguide 1407at the bend 1406 in a plane (x-z plane as shown) comprising the bend1406 of the film lightguide 1407 has a subtended angle 1405 from themidpoint 1404 of the line 1413 (shown dashed) between a point 1409 onthe inner surface 1410 of the film lightguide 1407 at the start of thebend 1406 and the point 1403 on the inner surface 1410 of the filmlightguide 1407 at the end of the bend 1406. In this embodiment, thesubtended angle 1405 is 90 degrees and the radius of curvature 1411 ofthe surface 1401 of the guide 1402 adjacent the inner surface 1410 ofthe film lightguide 1407 in the plane (x-z plane) comprising the bend1406 is greater than 1.5 times the thickness 1412 of the reflectivespatial light modulator 1408.

FIG. 15 is a side view of one embodiment of a reflective display 1500including a film lightguide 1507 operatively coupled to a reflectivespatial light modulator 1408. A plurality of coupling lightguides 104extend from the film lightguide 1407 and are folded and stacked suchthat their ends 206 are positioned to receive light from the lightsource 102. A relative position maintaining element 207 substantiallymaintains the relative position of the coupling lightguides 104. Thefilm lightguide 1507 includes a first bend 1506 in the light mixingregion 219 such that a portion 218 of the light mixing region 219 ispositioned behind the light emitting region 108 of the film lightguide1507 and reflective spatial light modulator 1408. A guide 1502 ispositioned within the first bend 1506 such that a first curved surface1501 of the guide 1502 is adjacent the inner surface 1510 of the filmlightguide 1507. In this embodiment, the curved surface 1501 of theguide 1502 adjacent the inner surface 1510 of the film lightguide 1507at the bend 1506 in a plane (x-z plane as shown) comprising the bend1506 of the film lightguide 1507 has a subtended angle 1505 from themidpoint 1504 of the line 1513 (shown dashed) between a point 1509 onthe inner surface 1510 of the film lightguide 1507 at the start of thebend 1506 and the point 1503 on the inner surface 1510 of the filmlightguide 1507 at the end of the bend 1506. In this embodiment, thesubtended angle 1505 is 180 degrees and the radius of curvature 1511 ofthe surface 1501 of the guide 1502 adjacent the inner surface 1510 ofthe film lightguide 1507 in the plane (x-z plane) comprising the bend1506 is greater than the thickness 1412 of the reflective spatial lightmodulator 1408.

FIG. 16 is a side view of one embodiment of a reflective display 1600including a film lightguide 1607 operatively coupled to a reflectivespatial light modulator 1408. A plurality of coupling lightguides 104extend from the film lightguide 1407 and are folded and stacked suchthat their ends 206 are positioned to receive light from the lightsource 102. A relative position maintaining element 207 substantiallymaintains the relative position of the coupling lightguides 104. Thefilm lightguide 1607 includes a first bend 1606 in the light mixingregion 219 such that a portion 218 of the light mixing region 219 ispositioned behind the light emitting region 108 of the film lightguide1607 and reflective spatial light modulator 1408. A guide 1602 ispositioned within the first bend 1606 such that a first curved surface1601 of the guide 1602 is adjacent the inner surface 1610 of the filmlightguide 1607. In this embodiment, the curved surface 1601 of theguide 1602 adjacent the inner surface 1610 of the film lightguide 1607at the bend 1606 in a plane (x-z plane as shown) comprising the bend1606 of the film lightguide 1607 has a subtended angle 1605 from themidpoint 1604 of the line 1613 (shown dashed) between a point 1609 onthe inner surface 1610 of the film lightguide 1607 at the start of thebend 1606 and the point 1603 on the inner surface 1610 of the filmlightguide 1607 at the end of the bend 1606. In this embodiment, thesubtended angle 1605 is 270 degrees.

In one aspect, a lightguide comprises a film including a body comprisinga light emitting region and a light mixing region adjacent the lightemitting region, a first bend formed in the film within the light mixingregion having a first diameter in a first plane, wherein a first portionof the light mixing region is positioned behind the light emittingregion, and a second bend formed in the film within the light mixingregion, wherein a second portion of the light mixing region ispositioned at a distance from the light emitting region less than thefirst diameter. In another embodiment, a lightguide comprises a filmincluding a body having a first surface and an opposing second surfaceand a plurality of coupling lightguides extending from the body, eachcoupling lightguide of the plurality of coupling lightguides having anend, the plurality of coupling lightguides are folded and stacked suchthat the ends of the plurality of coupling lightguides define a lightinput surface; the body of the film comprises a light emitting regiondefined by a plurality of light extracting features and a light mixingregion positioned between the plurality of coupling lightguides and thelight emitting region, the light mixing region folded behind the lightemitting region at a first bend with a first bend diameter in a firstplane, wherein the first bend diameter is greater than an averageseparation between the first surface of the film within the lightemitting region and the first surface of the film within the lightmixing region positioned behind the light emitting region.

In another aspect, the ratio of a length of the light mixing region to alength of the light emitting region in the first plane is greater than0.1. In a further aspect, the light mixing region comprises a secondbend in a first plane between the first bend and the plurality ofcoupling lightguides, the second bend positioning a portion of the lightmixing region at a distance from the light emitting region less than thefirst bend diameter.

In a further aspect, a lightguide comprises a film including a bodycomprising a light emitting region and a light mixing region adjacentthe light emitting region; a first bend with a first diameter in a firstplane formed in the film within the light mixing region, wherein a firstportion of the light mixing region is positioned behind the lightemitting region; and a second bend formed in the film within the lightmixing region.

In one aspect, a light emitting device including a film-based lightguidewith coupling lightguides extending therefrom includes a frame includingone or more attachment mechanisms, wherein the lightguide is operativelycoupled to the frame. In another aspect, the frame includes a pluralityof attachment mechanisms on one or more sides or internal regions thatfacilitate the coupling of one or more components of the light emittingdevice to the frame. In one aspect, the attachment mechanism includesone or more tabs operatively coupled to one or more coupling lightguiderelative position maintaining elements. In another aspect, the frameincludes a support arm including one or more attachment mechanisms,wherein the support arm extends into the interior region or exteriorregion of the frame. In one aspect, the frame is thermally coupled toone or more light sources of the light emitting device and functions asa heat sink for the one or more light sources.

In one aspect, a film-based lightguide operatively coupled to the frameincludes a first bend to fold a light mixing region of the lightguidebehind the frame to position at least one of a light source, a lightinput coupler, and the relative position maintaining element behind thelight emitting region of the lightguide. In this embodiment, thelightguide includes a second bend that positions at least one of thelight source, the light input coupler, and the relative positionmaintaining element at a distance from the light emitting region of thelightguide in the thickness direction less than a diameter of the firstbend. In another aspect, a large first bend in the lightguide (such as afirst bend with a first bend angle greater than 180 degrees) positionsat least one of the light source, the light input coupler, and therelative position maintaining element closer to the light emittingregion and behind the light emitting region of the lightguide. In oneaspect, the lightguide includes one or more bends or folds wherein eachbend may bend the lightguide closer to another region of the lightguideand/or fold one region of the lightguide upon (or behind or above)another region of the lightguide. In one aspect, the lightguide includestwo or more bends and the ratio of the length of the light mixing regionto the length of the light emitting region of the lightguide is greaterthan one selected from the group: 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4,1.6, 1.8, 2, 3, and 4. In one aspect, a method of manufacturing a lightemitting device includes bending a film-based lightguide at a first bendwith a first bend diameter such that a portion of the light mixingregion is disposed behind the light emitting region of the lightguideand the distance between the light emitting region of the lightguide andthe portion of the light mixing region behind the light emitting regionis less than the first bend diameter.

Exemplary embodiments of light emitting devices and methods for makingor producing the same are described above in detail. The devices,components, and methods are not limited to the specific embodimentsdescribed herein, but rather, the devices, components of the devicesand/or steps of the methods may be utilized independently and separatelyfrom other devices, components and/or steps described herein. Further,the described devices, components and/or the described methods steps canalso be defined in, or used in combination with, other devices and/ormethods, and are not limited to practice with only the devices andmethods as described herein.

While the disclosure includes various specific embodiments, thoseskilled in the art will recognize that the embodiments can be practicedwith modification within the spirit and scope of the disclosure and theclaims.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, numerous equivalents to thespecific procedures described herein. Such equivalents are considered tobe within the scope of the disclosure. Various substitutions,alterations, and modifications may be made to the embodiments withoutdeparting from the spirit and scope of the disclosure. Other aspects,advantages, and modifications are within the scope of the disclosure.This disclosure is intended to cover any adaptations or variations ofthe specific embodiments discussed herein. Therefore, it is intendedthat this disclosure be limited only by the claims and the equivalentsthereof.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified by the term “about”. Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe foregoing specification and attached claims are approximations thatcan vary depending upon the desired properties sought to be obtained bythose skilled in the art utilizing the teachings disclosed herein.Unless indicated to the contrary, all tests and properties are measuredat an ambient temperature of 25 degrees Celsius or the environmentaltemperature within or near the device when powered on (when indicated)under constant ambient room temperature of 25 degrees Celsius.

What is claimed is:
 1. A lightguide comprising: a film including a bodyhaving a first surface and an opposing second surface and a plurality ofcoupling lightguides extending from the body, each coupling lightguideof the plurality of coupling lightguides having an end, the plurality ofcoupling lightguides folded and stacked such that the ends of theplurality of coupling lightguides define a light input surface; the bodyof the film comprising a light emitting region defined by a plurality oflight extracting features and a light mixing region positioned betweenthe plurality of coupling lightguides and the light emitting region, thelight mixing region folded behind the light emitting region at a firstbend with a first bend diameter in a first plane, wherein the first benddiameter is greater than an average separation between the first surfaceof the film within the light emitting region and the first surface ofthe film within the light mixing region positioned behind the lightemitting region.
 2. The lightguide of claim 1 wherein a shape of thefilm in the first plane comprises an inflection point in the lightmixing region.
 3. The lightguide of claim 1 wherein a ratio of a lengthof the light mixing region to a length of the light emitting region inthe first plane is greater than 0.1.
 4. The lightguide of claim 1wherein a ratio of a length of the light mixing region to a length ofthe light emitting region in the first plane is greater than
 1. 5. Thelightguide of claim 1 wherein a ratio of a length of the light mixingregion to a length of the light emitting region in the first plane isgreater than 2 and the film is folded behind itself at least twice. 6.The lightguide of claim 1 wherein the first bend has a first bend anglegreater than 180 degrees.
 7. The lightguide of claim 1 wherein the lightmixing region comprises a second bend in the first plane between thefirst bend and the plurality of coupling lightguides, the second bendpositioning a portion of the light mixing region at a distance from thelight emitting region less than the first bend diameter.
 8. Thelightguide of claim 1 wherein the light mixing region comprises a secondbend in the first plane such that a portion of the light mixing regionis positioned at a distance from the light emitting region less than thefirst bend diameter.
 9. The lightguide of claim 8 wherein the lightmixing region comprises a third bend in the first plane.
 10. Thelightguide of claim 9 wherein the portion of the light mixing region isparallel to the light emitting region.
 11. A lightguide comprising: afilm including a body comprising a light emitting region and a lightmixing region adjacent the light emitting region; a first bend formed inthe film within the light mixing region having a first diameter in afirst plane, wherein a first portion of the light mixing region ispositioned behind the light emitting region and a second bend formed inthe film within the light mixing region in the first plane, the secondbend positions the first portion of the light mixing region at adistance from the light emitting region less than the first diameter.12. The lightguide of claim 11 further comprising a plurality ofcoupling lightguides extending from the light mixing region.
 13. Thelightguide of claim 11 wherein a shape of the film in the first planecomprises an inflection point in the light mixing region.
 14. Thelightguide of claim 11 wherein a ratio of a length of the light mixingregion to a length of the light emitting region in the first plane isgreater than 0.1.
 15. The lightguide of claim 11 wherein a ratio of alength of the light mixing region to a length of the light emittingregion in the first plane is greater than
 1. 16. The lightguide of claim11 wherein the first diameter is greater than an average separationbetween a first surface of the film within the light emitting region andthe first surface of the film within the first portion of the lightmixing region.
 17. The lightguide of claim 16 wherein a portion of thelight mixing region is parallel to the light emitting region.
 18. Alightguide comprising: a film including a body comprising a lightemitting region and a light mixing region adjacent the light emittingregion; a first bend with a first diameter in a first plane formed inthe film within the light mixing region, wherein the first bendpositions a first portion of the light mixing region behind the lightemitting region; and a second bend formed in the film within the lightmixing region, wherein the first bend has a first bend angle of at least180 degrees and the second bend has a second bend angle of at least 180degrees.
 19. The lightguide of claim 18 wherein the second bend folds asecond portion of the light mixing region behind the first portion ofthe light mixing region.